# OpcSubscription Members > Reference: Provides mechanisms to monitor a set of attributes (= node data) and (node-related) events using notifications being reported from the server to the client.
Type
OpcSubscription
Namespace
Opc.UaFx.Client
Assembly
Opc.UaFx.Advanced.dll
Package
Opc.UaFx.Advanced v2.59.0
Also in
Opc.UaFx.Client
## Properties ### Client since v2.15 Gets the [OpcClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/) used to setup this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public OpcClient Client { get; } ```
```vbnet Public ReadOnly Property Client As OpcClient ```
**Property value** [OpcClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/) An instance of the [OpcClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/) class used to setup this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). ### CurrentKeepAliveCount Gets the actual keep-alive count used by the server for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) which has been negotiated by the server against the [KeepAliveCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#keepalivecount) requested to meet its own constraints.
```csharp public long CurrentKeepAliveCount { get; } ```
```vbnet Public ReadOnly Property CurrentKeepAliveCount As Long ```
**Property value** [Int64](https://learn.microsoft.com/dotnet/api/system.int64) The negoiated and actual [KeepAliveCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#keepalivecount) used. **Remarks** The server negotiates the value up or down to meet its own constraints. ### CurrentLifetimeCount Gets the actual lifetime count used by the server for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) which has been negotiated by the server against the [LifetimeCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#lifetimecount) requested to meet its own constraints.
```csharp public long CurrentLifetimeCount { get; } ```
```vbnet Public ReadOnly Property CurrentLifetimeCount As Long ```
**Property value** [Int64](https://learn.microsoft.com/dotnet/api/system.int64) The negoiated and actual [LifetimeCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#lifetimecount) used. **Remarks** The server negotiates the value up or down to meet its own constraints. ### CurrentPriority Gets the actual relative priority of the subscription used to priorize notifications being send then more than one subscription is to be notified.
```csharp public int CurrentPriority { get; } ```
```vbnet Public ReadOnly Property CurrentPriority As Integer ```
**Property value** [Int32](https://learn.microsoft.com/dotnet/api/system.int32) The actual [Priority](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#priority) used. **Remarks** For more details see [Priority](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#priority). ### CurrentPublishingInterval Gets the actual publishing interval used by the server for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) which has been negotiated by the server against the [PublishingInterval](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#publishinginterval) requested to meet its own constraints.
```csharp public double CurrentPublishingInterval { get; } ```
```vbnet Public ReadOnly Property CurrentPublishingInterval As Double ```
**Property value** [Double](https://learn.microsoft.com/dotnet/api/system.double) The negoiated and actual [PublishingInterval](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#publishinginterval) used. **Remarks** The server negotiates the value up or down to meet its own constraints. ### CurrentPublishingIsEnabled Gets the actual value indicating whether publishing is enabled by the server for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) which has been created and validated by the server against its own constraints.
```csharp public bool CurrentPublishingIsEnabled { get; } ```
```vbnet Public ReadOnly Property CurrentPublishingIsEnabled As Boolean ```
**Property value** [Boolean](https://learn.microsoft.com/dotnet/api/system.boolean) The value true if the server has enabled publishing for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/); otherwise the value false. ### DisplayName Gets or sets the name of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) used just for display purpose in the client application.
```csharp public string DisplayName { get; set; } ```
```vbnet Public Property DisplayName As String ```
**Property value** [String](https://learn.microsoft.com/dotnet/api/system.string) The name of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) used just for display purpose in the client application. ### HasPendingChanges Gets a value indicating whether there exists any pending change on the subscription which needs to be applied to take effect ([ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges)).
```csharp public bool HasPendingChanges { get; } ```
```vbnet Public ReadOnly Property HasPendingChanges As Boolean ```
**Property value** [Boolean](https://learn.microsoft.com/dotnet/api/system.boolean) The value true if there is at least one change not yet applied; otherwise the value false. ### Id Gets the server-assigned unique identifier for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public long Id { get; } ```
```vbnet Public ReadOnly Property Id As Long ```
**Property value** [Int64](https://learn.microsoft.com/dotnet/api/system.int64) The server-assigned unique identifier for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). **Remarks** The identifier shall be unique for the entire server, not just for the Session, in order to allow the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) to be transferred to another session. ### IsCreated Gets a value indicating whether this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has been created on the server.
```csharp public bool IsCreated { get; } ```
```vbnet Public ReadOnly Property IsCreated As Boolean ```
**Property value** [Boolean](https://learn.microsoft.com/dotnet/api/system.boolean) The value true if the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has been created on the server; otherwise the value false. **Remarks** When the client reconnects with a new session, it creates its subscriptions again. A subscription the server rejects then is not created, while the client is connected again with the others; it is created again with the next new session. ### IsPublishing Gets a value indicating whether this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) is receiving notifications.
```csharp public bool IsPublishing { get; } ```
```vbnet Public ReadOnly Property IsPublishing As Boolean ```
**Property value** [Boolean](https://learn.microsoft.com/dotnet/api/system.boolean) The value true if the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) is receiving notifications; otherwise the value false. ### KeepAliveCount Gets or sets a value which defines the requested number of times the publishing timer have to expire without any notification being sent before the server have to send a keep-alive message to the client.
```csharp public long KeepAliveCount { get; set; } ```
```vbnet Public Property KeepAliveCount As Long ```
**Property value** [Int64](https://learn.microsoft.com/dotnet/api/system.int64) A value of zero indicates that the server have to revise the smallest supported keep-alive count. The default value of this property is 10. The value of this property configures the keep-alive counter that counts the number of consecutive publishing cycles in which there have been no notifications to report to the client. When the maximum keep-alive count is reached, a publish request is de-queued and used to return a keep-alive message. This keep-alive message informs the client that the subscription is still active. The maximum keep-alive count may be subsequently modified. If there are no publish requests queued, the server waits for the next one to be received and sends the keep-alive immediately without waiting for the next publishing cycle. The value of the underlying property is an [uint](https://learn.microsoft.com/dotnet/api/system.uint32) which is covered using a [long](https://learn.microsoft.com/dotnet/api/system.int64) to assure CLS compliance. In fact this restricts the value range of this property to [MinValue](https://learn.microsoft.com/dotnet/api/system.uint32.minvalue) and [MaxValue](https://learn.microsoft.com/dotnet/api/system.uint32.maxvalue). **Remarks** The server needs to be notified about changes to this property to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. ### LastNotification Gets the last notification received from the server.
```csharp public OpcNotification LastNotification { get; } ```
```vbnet Public ReadOnly Property LastNotification As OpcNotification ```
**Property value** [OpcNotification](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnotification/) An instance of the [OpcNotification](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnotification/) class which represents the last notfication received from the server or a null reference (Nothing in Visual Basic) if the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet received a notification from the server or [MaxMessageCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#maxmessagecount) is less or equals zero. ### LastNotificationTime Gets the time the last notification which has been received from the server.
```csharp public DateTime? LastNotificationTime { get; } ```
```vbnet Public ReadOnly Property LastNotificationTime As Date? ```
**Property value** [Nullable](https://learn.microsoft.com/dotnet/api/system.nullable-1)<[DateTime](https://learn.microsoft.com/dotnet/api/system.datetime)> A [DateTime](https://learn.microsoft.com/dotnet/api/system.datetime) identifying the instant of time the last notification which has been received from the server or a null reference (Nothing in Visual Basic) if the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet received a notification from the server. ### LifetimeCount Gets or sets a value which defines the requested number of times the publishing timer have to expire without any publish request before the server have to delete this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public long LifetimeCount { get; set; } ```
```vbnet Public Property LifetimeCount As Long ```
**Property value** [Int64](https://learn.microsoft.com/dotnet/api/system.int64) The number of times the publishing timer have to expire without any publish request. A recommended value is at least a minimum of three times of the [KeepAliveCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#keepalivecount). The default value of this property is 100. **Remarks** The value of the underlying property is an [uint](https://learn.microsoft.com/dotnet/api/system.uint32) which is covered using a [long](https://learn.microsoft.com/dotnet/api/system.int64) to assure CLS compliance. In fact this restricts the value range of this property to [MinValue](https://learn.microsoft.com/dotnet/api/system.uint32.minvalue) and [MaxValue](https://learn.microsoft.com/dotnet/api/system.uint32.maxvalue). The server needs to be notified about changes to this property to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. ### MaxMessageCount Gets or sets the maximum number of notifications to keep in the cache.
```csharp public int MaxMessageCount { get; set; } ```
```vbnet Public Property MaxMessageCount As Integer ```
**Property value** [Int32](https://learn.microsoft.com/dotnet/api/system.int32) The maximum number of notification to keep in the cache. The default value of this property is 10. ### MaxNotificationsPerPublish Gets or sets a value which defines the maximum number of notifications that the client wants to receive in a single publish response.
```csharp public long MaxNotificationsPerPublish { get; set; } ```
```vbnet Public Property MaxNotificationsPerPublish As Long ```
**Property value** [Int64](https://learn.microsoft.com/dotnet/api/system.int64) The maximum number of notifications that the client wants to receive in a single publish response. The number of notifications per publish is the sum of [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) in a data change related notification and the number of events in an event notification. The default value of this property is 1000. **Remarks** A value of zero indicates that there is no limit. The value of the underlying property is an [uint](https://learn.microsoft.com/dotnet/api/system.uint32) which is covered using a [long](https://learn.microsoft.com/dotnet/api/system.int64) to assure CLS compliance. In fact this restricts the value range of this property to [MinValue](https://learn.microsoft.com/dotnet/api/system.uint32.minvalue) and [MaxValue](https://learn.microsoft.com/dotnet/api/system.uint32.maxvalue). ### MinLifetimeInterval Gets or sets a value which defines the minimum lifetime interval to apply in respect of the [PublishingInterval](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#publishinginterval) and the [LifetimeCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#lifetimecount) configured.
```csharp public long MinLifetimeInterval { get; set; } ```
```vbnet Public Property MinLifetimeInterval As Long ```
**Property value** [Int64](https://learn.microsoft.com/dotnet/api/system.int64) The interval which should be a multiple of the [PublishingInterval](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#publishinginterval) to assure that the [LifetimeCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#lifetimecount) requested is sensible enough to get covered within the [PublishingInterval](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#publishinginterval). ### MonitoredItems Gets a read-only collection of [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) instances associated with this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public OpcMonitoredItemReadOnlyCollection MonitoredItems { get; } ```
```vbnet Public ReadOnly Property MonitoredItems As OpcMonitoredItemReadOnlyCollection ```
**Property value** [OpcMonitoredItemReadOnlyCollection](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditemreadonlycollection/) An instance of the [OpcMonitoredItemReadOnlyCollection](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditemreadonlycollection/) class. **Remarks** Use the monitored item related methods of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) to manipulate the items contained in the collection offered by this property. ### Notifications Gets a sequence of [OpcNotification](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnotification/) instances received from the server.
```csharp public IEnumerable Notifications { get; } ```
```vbnet Public ReadOnly Property Notifications As IEnumerable(Of OpcNotification) ```
**Property value** [IEnumerable](https://learn.microsoft.com/dotnet/api/system.collections.generic.ienumerable-1)<[OpcNotification](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnotification/)> A sequence of [OpcNotification](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnotification/) instances representing the notifications received from the server. The sequence is empty if the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet received a notification from the server. **Remarks** The number of instances in the sequence is limited to the maximum number of messages in the cache (see [MaxMessageCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#maxmessagecount)). ### Priority Gets or sets a value which defines the relative priority of the subscription used to priorize notifications being send then more than one subscription is to be notified.
```csharp public int Priority { get; set; } ```
```vbnet Public Property Priority As Integer ```
**Property value** [Int32](https://learn.microsoft.com/dotnet/api/system.int32) The relative priority of the subscription to notify. **Remarks** In case of subscriptions with equal priority the server shall send the notifications in a round-robin fashion. A client that does not require special priority settings should set this value to zero. The value of the underlying property is a [byte](https://learn.microsoft.com/dotnet/api/system.byte) which is covered using an [int](https://learn.microsoft.com/dotnet/api/system.int32) to assure an even API level. In fact this restricts the value range of this property to [MinValue](https://learn.microsoft.com/dotnet/api/system.byte.minvalue) and [MaxValue](https://learn.microsoft.com/dotnet/api/system.byte.maxvalue). The server needs to be notified about changes to this property to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. ### PublishingInterval Gets or sets the requested number of milliseconds of the interval within the server have to send cyclic notifications to the client.
```csharp public int PublishingInterval { get; set; } ```
```vbnet Public Property PublishingInterval As Integer ```
**Property value** [Int32](https://learn.microsoft.com/dotnet/api/system.int32) The interval within the server have to send cyclic notifications to the client. A value of zero or negative indicates that the server have to revise the fastest supported publishing interval. **Remarks** The publishing interval of a subscription defines the cyclic rate at which the subscription executes. Each time it executes, it attempts to send a message to the client. Messages contain notifications that have not yet been reported to client. The negotiated value of this property is used as the default sampling interval for the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) assigned to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). The server needs to be notified about changes to this property to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. ### PublishingIsEnabled Gets or sets a value indicating whether publishing is enabled for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public bool PublishingIsEnabled { get; set; } ```
```vbnet Public Property PublishingIsEnabled As Boolean ```
**Property value** [Boolean](https://learn.microsoft.com/dotnet/api/system.boolean) The value true if publishing is enabled for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/); otherwise the value false. The default value of this property is true. **Remarks** The value of this property does not affect the value of the monitoring mode property of the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems). The server needs to be notified about changes to this property to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. ### PublishTime Gets the time the last notification was published from the server.
```csharp public DateTime? PublishTime { get; } ```
```vbnet Public ReadOnly Property PublishTime As Date? ```
**Property value** [Nullable](https://learn.microsoft.com/dotnet/api/system.nullable-1)<[DateTime](https://learn.microsoft.com/dotnet/api/system.datetime)> A [DateTime](https://learn.microsoft.com/dotnet/api/system.datetime) identifying the instant of time the last notification has been published from the server or a null reference (Nothing in Visual Basic) if the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet received a notification from the server or [MaxMessageCount](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#maxmessagecount) is less or equals zero. ### ReceivedDataChangeCallback Gets or sets the callback used to process data changes of the monitored items associated with this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public OpcDataChangeReceivedCallback ReceivedDataChangeCallback { get; set; } ```
```vbnet Public Property ReceivedDataChangeCallback As OpcDataChangeReceivedCallback ```
**Property value** [OpcDataChangeReceivedCallback](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedcallback/) A [OpcDataChangeReceivedCallback](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedcallback/) used to process data change items. The value can also be a null reference (Nothing in Visual Basic). **Remarks** Use this property to directly handle all data change items without to rely on the chain of registered event handlers. ### ReceivedEventCallback Gets or sets the callback used to process events of the monitored items associated with this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public OpcEventReceivedCallback ReceivedEventCallback { get; set; } ```
```vbnet Public Property ReceivedEventCallback As OpcEventReceivedCallback ```
**Property value** [OpcEventReceivedCallback](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedcallback/) A [OpcDataChangeReceivedCallback](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedcallback/) used to process event items. The value can also be a null reference (Nothing in Visual Basic). **Remarks** Use this property to directly handle all event items without to rely on the chain of registered event handlers. ### SequenceNumber Gets the sequence number of the last notification which has been received from the server.
```csharp public long? SequenceNumber { get; } ```
```vbnet Public ReadOnly Property SequenceNumber As Long? ```
**Property value** [Nullable](https://learn.microsoft.com/dotnet/api/system.nullable-1)<[Int64](https://learn.microsoft.com/dotnet/api/system.int64)> The [SequenceNumber](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnotification/members#sequencenumber) of the last notification which has been received from the server or a null reference (Nothing in Visual Basic) if the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet received a notification from the server. ### Tag Gets or sets the object that contains additional user data about the subscription.
```csharp public object Tag { get; set; } ```
```vbnet Public Property Tag As Object ```
**Property value** [Object](https://learn.microsoft.com/dotnet/api/system.object) An [object](https://learn.microsoft.com/dotnet/api/system.object) that contains additional user data about the subscription. The default is null (Nothing in Visual Basic). ### TimestampsToReturn Gets or sets the timestamps the server shall transmit for each monitored item.
```csharp public OpcTimestampsToReturn TimestampsToReturn { get; set; } ```
```vbnet Public Property TimestampsToReturn As OpcTimestampsToReturn ```
**Property value** [OpcTimestampsToReturn](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opctimestampstoreturn/) One of the members defined by the [OpcTimestampsToReturn](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opctimestampstoreturn/) enumeration. The default value of this property is [Both](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opctimestampstoreturn/#both). **Remarks** The "timestamps to return" criteria is only applied to [OpcValue](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcvalue/) instances. This means that in case of monitoring events only event fields of the type [OpcValue](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcvalue/) are effected by the value of this property. The server needs to be notified about changes to this property to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. ### UseMonitoredItemDataCache Gets or sets a value indicating whether this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) shall forward notifications received from the server to monitored item individual caches. This enables the monitored items to process the data changes and event fields on their own.
```csharp public bool UseMonitoredItemDataCache { get; set; } ```
```vbnet Public Property UseMonitoredItemDataCache As Boolean ```
**Property value** [Boolean](https://learn.microsoft.com/dotnet/api/system.boolean) The value true if the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) instances associated with this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) receive their own item-related notification and can process the notification data on their own; otherwise the value false. The default value of this property is true. ## Methods ### AddMonitoredItem 15 overloads | Overload | Description | |---|---| | [AddMonitoredItem(OpcMonitoredItem)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-client-opcmonitoreditem) | Adds the monitored item specified by `item` to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). | | [AddMonitoredItem(OpcNodeId)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid)since v2.7 | Adds a new monitored item which subscribes to changes on the [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute of the node specified by `nodeId`. | | [AddMonitoredItem(OpcNodeId, OpcDataChangeReceivedEventHandler)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-client-opcdatachangereceivedeventhandler)since v2.7 | Adds a new monitored item which subscribes to changes on the [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute of the node specified by `nodeId`. | | [AddMonitoredItem(OpcNodeId, OpcEventReceivedEventHandler)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-client-opceventreceivedeventhandler)since v2.7 | Adds a new monitored item which subscribes to events on the [EventNotifier](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#eventnotifier) attribute of the node specified by `nodeId`. | | [AddMonitoredItem(OpcNodeId, OpcAttribute)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opcattribute)since v2.7 | Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId`. | | [AddMonitoredItem(OpcNodeId, OpcAttribute, OpcDataChangeReceivedEventHandler)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opcattribute-opc-uafx-client-opcdatachangereceivedeventhandler)since v2.7 | Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId`. | | [AddMonitoredItem(OpcNodeId, OpcAttribute, OpcEventReceivedEventHandler)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opcattribute-opc-uafx-client-opceventreceivedeventhandler)since v2.7 | Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId`. | | [AddMonitoredItem(OpcNodeId, OpcMonitoringFilter)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opcmonitoringfilter)since v2.7 | Adds a new monitored item which subscribes to changes on the [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute of the node specified by `nodeId` using the further configured `filter`. | | [AddMonitoredItem(OpcNodeId, OpcDataChangeFilter, OpcDataChangeReceivedEventHandler)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opcdatachangefilter-opc-uafx-client-opcdatachangereceivedeventhandler)since v2.7 | Adds a new monitored item which subscribes to changes on the [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute of the node specified by `nodeId` using the further configured `filter`. | | [AddMonitoredItem(OpcNodeId, OpcEventFilter, OpcEventReceivedEventHandler)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opceventfilter-opc-uafx-client-opceventreceivedeventhandler)since v2.7 | Adds a new monitored item which subscribes to changes on the [EventNotifier](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#eventnotifier) attribute of the node specified by `nodeId` using the further configured `filter`. | | [AddMonitoredItem(OpcNodeId, OpcAttribute, OpcMonitoringFilter)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opcattribute-opc-uafx-opcmonitoringfilter)since v2.7 | Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId` using the further configured `filter`. | | [AddMonitoredItem(OpcNodeId, OpcAttribute, OpcDataChangeFilter, OpcDataChangeReceivedEventHandler)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opcattribute-opc-uafx-opcdatachangefilter-opc-uafx-client-opcdatachangereceivedeventhandler)since v2.7 | Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId` using the further configured `filter`. | | [AddMonitoredItem(OpcNodeId, OpcAttribute, OpcEventFilter, OpcEventReceivedEventHandler)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-opc-uafx-opcnodeid-opc-uafx-opcattribute-opc-uafx-opceventfilter-opc-uafx-client-opceventreceivedeventhandler)since v2.7 | Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId` using the further configured `filter`. | | [AddMonitoredItem(IEnumerable<OpcMonitoredItem>)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#addmonitoreditem-system-collections-generic-ienumerable-of-opc-uafx-client-opcmonitoreditem) | Adds the monitored items specified by `items` to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). | | [AddMonitoredItem(params OpcMonitoredItem\[\])](#addmonitoreditem-opc-uafx-client-opcmonitoreditem-array) | Adds the monitored items specified by `items` to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). | #### AddMonitoredItem(OpcMonitoredItem) Adds the monitored item specified by `item` to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public void AddMonitoredItem(OpcMonitoredItem item) ```
```vbnet Public Sub AddMonitoredItem(item As OpcMonitoredItem) ```
**Parameters** | Name | Type | Description | |---|---|---| | `item` | [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) | The [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) to add. | **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `item` is a null reference (Nothing in Visual Basic). | #### AddMonitoredItem(OpcNodeId) since v2.7 Adds a new monitored item which subscribes to changes on the [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute of the node specified by `nodeId`.
```csharp public OpcMonitoredItem AddMonitoredItem(OpcNodeId nodeId) ```
```vbnet Public Function AddMonitoredItem(nodeId As OpcNodeId) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute is to be monitored. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcDataChangeReceivedEventHandler) since v2.7 Adds a new monitored item which subscribes to changes on the [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute of the node specified by `nodeId`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcDataChangeReceivedEventHandler received) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, received As OpcDataChangeReceivedEventHandler) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute is to be monitored. | | `received` | [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) | The [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) method to assign as the event handler of the [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#datachangereceived) event or a null reference (Nothing in Visual Basic) if there no event handler is to be assigned first. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcEventReceivedEventHandler) since v2.7 Adds a new monitored item which subscribes to events on the [EventNotifier](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#eventnotifier) attribute of the node specified by `nodeId`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcEventReceivedEventHandler received) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, received As OpcEventReceivedEventHandler) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its [EventNotifier](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#eventnotifier) attribute is to be monitored. | | `received` | [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) | The [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) method to assign as the event handler of the [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#eventreceived) event or a null reference (Nothing in Visual Basic) if there no event handler is to be assigned first. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcAttribute) since v2.7 Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcAttribute attribute) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, attribute As OpcAttribute) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its `attribute` is to be monitored. | | `attribute` | [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) | The [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) to monitor. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcAttribute, OpcDataChangeReceivedEventHandler) since v2.7 Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcAttribute attribute, OpcDataChangeReceivedEventHandler received) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, attribute As OpcAttribute, received As OpcDataChangeReceivedEventHandler) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its `attribute` is to be monitored. | | `attribute` | [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) | The [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) to monitor. | | `received` | [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) | The [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) method to assign as the event handler of the [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#datachangereceived) event or a null reference (Nothing in Visual Basic) if there no event handler is to be assigned first. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcAttribute, OpcEventReceivedEventHandler) since v2.7 Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcAttribute attribute, OpcEventReceivedEventHandler received) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, attribute As OpcAttribute, received As OpcEventReceivedEventHandler) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its `attribute` is to be monitored. | | `attribute` | [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) | The [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) to monitor. | | `received` | [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) | The [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) method to assign as the event handler of the [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#eventreceived) event or a null reference (Nothing in Visual Basic) if there no event handler is to be assigned first. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcMonitoringFilter) since v2.7 Adds a new monitored item which subscribes to changes on the [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute of the node specified by `nodeId` using the further configured `filter`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcMonitoringFilter filter) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, filter As OpcMonitoringFilter) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute is to be monitored. | | `filter` | [OpcMonitoringFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringfilter/) | The [OpcMonitoringFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringfilter/) (either a [OpcDataChangeFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangefilter/) or a [OpcEventFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opceventfilter/)) to use to apply different conditions while monitoring the attribute. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcDataChangeFilter, OpcDataChangeReceivedEventHandler) since v2.7 Adds a new monitored item which subscribes to changes on the [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute of the node specified by `nodeId` using the further configured `filter`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcDataChangeFilter filter, OpcDataChangeReceivedEventHandler received) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, filter As OpcDataChangeFilter, received As OpcDataChangeReceivedEventHandler) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its [Value](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#value) attribute is to be monitored. | | `filter` | [OpcDataChangeFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangefilter/) | The [OpcDataChangeFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangefilter/) to use to apply different conditions while monitoring the attribute. | | `received` | [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) | The [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) method to assign as the event handler of the [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#datachangereceived) event or a null reference (Nothing in Visual Basic) if there no event handler is to be assigned first. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcEventFilter, OpcEventReceivedEventHandler) since v2.7 Adds a new monitored item which subscribes to changes on the [EventNotifier](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#eventnotifier) attribute of the node specified by `nodeId` using the further configured `filter`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcEventFilter filter, OpcEventReceivedEventHandler received) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, filter As OpcEventFilter, received As OpcEventReceivedEventHandler) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its [EventNotifier](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#eventnotifier) attribute is to be monitored. | | `filter` | [OpcEventFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opceventfilter/) | The [OpcEventFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opceventfilter/) to use to apply different conditions while monitoring the attribute. | | `received` | [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) | The [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) method to assign as the event handler of the [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#eventreceived) event or a null reference (Nothing in Visual Basic) if there no event handler is to be assigned first. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcAttribute, OpcMonitoringFilter) since v2.7 Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId` using the further configured `filter`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcAttribute attribute, OpcMonitoringFilter filter) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, attribute As OpcAttribute, filter As OpcMonitoringFilter) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its `attribute` is to be monitored. | | `attribute` | [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) | The [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) to monitor. | | `filter` | [OpcMonitoringFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringfilter/) | The [OpcMonitoringFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringfilter/) (either a [OpcDataChangeFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangefilter/) or a [OpcEventFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opceventfilter/)) to use to apply different conditions while monitoring the attribute. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcAttribute, OpcDataChangeFilter, OpcDataChangeReceivedEventHandler) since v2.7 Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId` using the further configured `filter`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcAttribute attribute, OpcDataChangeFilter filter, OpcDataChangeReceivedEventHandler received) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, attribute As OpcAttribute, filter As OpcDataChangeFilter, received As OpcDataChangeReceivedEventHandler) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its `attribute` is to be monitored. | | `attribute` | [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) | The [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) to monitor. | | `filter` | [OpcDataChangeFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangefilter/) | The [OpcDataChangeFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangefilter/) to use to apply different conditions while monitoring the attribute. | | `received` | [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) | The [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) method to assign as the event handler of the [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#datachangereceived) event or a null reference (Nothing in Visual Basic) if there no event handler is to be assigned first. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(OpcNodeId, OpcAttribute, OpcEventFilter, OpcEventReceivedEventHandler) since v2.7 Adds a new monitored item which subscribes to the `attribute` of the node specified by `nodeId` using the further configured `filter`.
```csharp public OpcMonitoredItem AddMonitoredItem( OpcNodeId nodeId, OpcAttribute attribute, OpcEventFilter filter, OpcEventReceivedEventHandler received) ```
```vbnet Public Function AddMonitoredItem( nodeId As OpcNodeId, attribute As OpcAttribute, filter As OpcEventFilter, received As OpcEventReceivedEventHandler) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `nodeId` | [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) | The [OpcNodeId](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodeid/) of the node its `attribute` is to be monitored. | | `attribute` | [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) | The [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) to monitor. | | `filter` | [OpcEventFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opceventfilter/) | The [OpcEventFilter](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opceventfilter/) to use to apply different conditions while monitoring the attribute. | | `received` | [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) | The [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) method to assign as the event handler of the [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#eventreceived) event or a null reference (Nothing in Visual Basic) if there no event handler is to be assigned first. | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) A new instance of the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) class setup with the information specified. The monitored item will then monitor the node identified by the values passed to this method. **Exceptions** | Exception | Condition | |---|---| | [ArgumentException](https://learn.microsoft.com/dotnet/api/system.argumentexception) | The `nodeId` is empty. | | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `nodeId` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(IEnumerable<OpcMonitoredItem>) Adds the monitored items specified by `items` to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public void AddMonitoredItem(IEnumerable items) ```
```vbnet Public Sub AddMonitoredItem(items As IEnumerable(Of OpcMonitoredItem)) ```
**Parameters** | Name | Type | Description | |---|---|---| | `items` | [IEnumerable](https://learn.microsoft.com/dotnet/api/system.collections.generic.ienumerable-1)<[OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/)> | A sequence of [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) istances to add. | **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `items` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### AddMonitoredItem(params OpcMonitoredItem\[\]) Adds the monitored items specified by `items` to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public void AddMonitoredItem(params OpcMonitoredItem[] items) ```
```vbnet Public Sub AddMonitoredItem(ParamArray items As OpcMonitoredItem()) ```
**Parameters** | Name | Type | Description | |---|---|---| | `items` | params [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/)[] | An array of [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) istances to add. | **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `items` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the new monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. ### ApplyChanges Applies any changes made on the current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) or on one of its [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) using the according services of the server connected to.
```csharp public void ApplyChanges() ```
```vbnet Public Sub ApplyChanges() ```
**Exceptions** | Exception | Condition | |---|---| | [InvalidOperationException](https://learn.microsoft.com/dotnet/api/system.invalidoperationexception) | The current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet been created (see [IsCreated](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#iscreated)). | | [OpcException](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcexception/) | The deletion, modification, creation of monitored items or the modification of the subscription has been failed. For more information see exception details. The following issues can lead to that exception: [BadNothingToDo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badnothingtodo), [BadTooManyOperations](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badtoomanyoperations), [BadTimestampsToReturnInvalid](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badtimestampstoreturninvalid), [BadSubscriptionIdInvalid](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badsubscriptionidinvalid) and [BadMonitoredItemIdInvalid](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badmonitoreditemidinvalid). | ### ChangeMonitoringMode 3 overloads | Overload | Description | |---|---| | [ChangeMonitoringMode(OpcMonitoringMode)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#changemonitoringmode-opc-uafx-opcmonitoringmode)since v2.11 | Changes the monitoring mode of all [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems). | | [ChangeMonitoringMode(OpcMonitoringMode, IEnumerable<OpcMonitoredItem>)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#changemonitoringmode-opc-uafx-opcmonitoringmode-system-collections-generic-ienumerable-of-opc-uafx-client-opcmonitoreditem) | Changes the monitoring mode of one or more monitored items. | | [ChangeMonitoringMode(OpcMonitoringMode, params OpcMonitoredItem\[\])](#changemonitoringmode-opc-uafx-opcmonitoringmode-opc-uafx-client-opcmonitoreditem-array) | Changes the monitoring mode of one or more monitored items. | **Exceptions (all overloads)** | Exception | Condition | |---|---| | [InvalidOperationException](https://learn.microsoft.com/dotnet/api/system.invalidoperationexception) | The current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet been created (see [IsCreated](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#iscreated)). | | [OpcException](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcexception/) | Changing the monitoring mode has failed. For more information see exception details. The following issues can lead to that exception: [BadNothingToDo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badnothingtodo), [BadTooManyOperations](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badtoomanyoperations), [BadSubscriptionIdInvalid](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badsubscriptionidinvalid) and [BadMonitoringModeInvalid](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badmonitoringmodeinvalid). | #### ChangeMonitoringMode(OpcMonitoringMode) since v2.11 Changes the monitoring mode of all [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems).
```csharp public void ChangeMonitoringMode(OpcMonitoringMode monitoringMode) ```
```vbnet Public Sub ChangeMonitoringMode(monitoringMode As OpcMonitoringMode) ```
**Parameters** | Name | Type | Description | |---|---|---| | `monitoringMode` | [OpcMonitoringMode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringmode/) | The new [OpcMonitoringMode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringmode/) to apply on all [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). | **Remarks** The server does not need to be notified about the change to take effect, because of this method directly operates on the server. #### ChangeMonitoringMode(OpcMonitoringMode, IEnumerable<OpcMonitoredItem>) Changes the monitoring mode of one or more monitored items.
```csharp public void ChangeMonitoringMode( OpcMonitoringMode monitoringMode, IEnumerable items) ```
```vbnet Public Sub ChangeMonitoringMode( monitoringMode As OpcMonitoringMode, items As IEnumerable(Of OpcMonitoredItem)) ```
**Parameters** | Name | Type | Description | |---|---|---| | `monitoringMode` | [OpcMonitoringMode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringmode/) | The new [OpcMonitoringMode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringmode/) to apply on the `items` specified. | | `items` | [IEnumerable](https://learn.microsoft.com/dotnet/api/system.collections.generic.ienumerable-1)<[OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/)> | A sequence of [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) instances, assigned to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/), its monitoring mode is to be changed. | **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `items` is a null reference (Nothing in Visual Basic). | **Remarks** The server does not need to be notified about the change to take effect, because of this method directly operates on the server. #### ChangeMonitoringMode(OpcMonitoringMode, params OpcMonitoredItem\[\]) Changes the monitoring mode of one or more monitored items.
```csharp public void ChangeMonitoringMode( OpcMonitoringMode monitoringMode, params OpcMonitoredItem[] items) ```
```vbnet Public Sub ChangeMonitoringMode( monitoringMode As OpcMonitoringMode, ParamArray items As OpcMonitoredItem()) ```
**Parameters** | Name | Type | Description | |---|---|---| | `monitoringMode` | [OpcMonitoringMode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringmode/) | The new [OpcMonitoringMode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringmode/) to apply on the `items` specified. | | `items` | params [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/)[] | An array of [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) instances, assigned to this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/), its monitoring mode is to be changed. | **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `items` is a null reference (Nothing in Visual Basic). | **Remarks** The server does not need to be notified about the change to take effect, because of this method directly operates on the server. ### GetMonitoredItem Retrieves the [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) the `dataChange` specified belongs to.
```csharp public OpcMonitoredItem GetMonitoredItem(OpcDataChangeDataSetItem dataChange) ```
```vbnet Public Function GetMonitoredItem( dataChange As OpcDataChangeDataSetItem) As OpcMonitoredItem ```
**Parameters** | Name | Type | Description | |---|---|---| | `dataChange` | [OpcDataChangeDataSetItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangedatasetitem/) | The [OpcDataChangeDataSetItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangedatasetitem/) the according [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) is to be determined from the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). | **Returns** [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) The [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) instance which belongs to the `dataChange` specified or a null reference (Nothing in Visual Basic) if the monitored item referenced by the [OpcDataChangeDataSetItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatachangedatasetitem/) instance could not be determined. **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `dataChange` is a null reference (Nothing in Visual Basic). | ### OnChanged protected · virtual Raises the [Changed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#changed) event of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp protected virtual void OnChanged(OpcSubscriptionChangedEventArgs e) ```
```vbnet Protected Overridable Sub OnChanged(e As OpcSubscriptionChangedEventArgs) ```
**Parameters** | Name | Type | Description | |---|---|---| | `e` | [OpcSubscriptionChangedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscriptionchangedeventargs/) | The event data. | ### OnDataChangeReceived protected · virtual Raises the [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#datachangereceived) event of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp protected virtual void OnDataChangeReceived(OpcDataChangeReceivedEventArgs e) ```
```vbnet Protected Overridable Sub OnDataChangeReceived( e As OpcDataChangeReceivedEventArgs) ```
**Parameters** | Name | Type | Description | |---|---|---| | `e` | [OpcDataChangeReceivedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventargs/) | The event data. | ### OnEventReceived protected · virtual Raises the [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#eventreceived) event of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp protected virtual void OnEventReceived(OpcEventReceivedEventArgs e) ```
```vbnet Protected Overridable Sub OnEventReceived(e As OpcEventReceivedEventArgs) ```
**Parameters** | Name | Type | Description | |---|---|---| | `e` | [OpcEventReceivedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventargs/) | The event data. | ### OnIsPublishingChanged protected · virtual Raises the [IsPublishingChanged](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#ispublishingchanged) event of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp protected virtual void OnIsPublishingChanged(EventArgs e) ```
```vbnet Protected Overridable Sub OnIsPublishingChanged(e As EventArgs) ```
**Parameters** | Name | Type | Description | |---|---|---| | `e` | [EventArgs](https://learn.microsoft.com/dotnet/api/system.eventargs) | The event data. | ### OnNotificationFailed protected · virtual · since v2.57 Raises the [NotificationFailed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#notificationfailed) event of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp protected virtual void OnNotificationFailed(OpcNotificationFailedEventArgs e) ```
```vbnet Protected Overridable Sub OnNotificationFailed( e As OpcNotificationFailedEventArgs) ```
**Parameters** | Name | Type | Description | |---|---|---| | `e` | [OpcNotificationFailedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnotificationfailedeventargs/) | The event data. | ### OnNotificationReceived protected · virtual Raises the [NotificationReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#notificationreceived) event of the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp protected virtual void OnNotificationReceived( OpcNotificationReceivedEventArgs e) ```
```vbnet Protected Overridable Sub OnNotificationReceived( e As OpcNotificationReceivedEventArgs) ```
**Parameters** | Name | Type | Description | |---|---|---| | `e` | [OpcNotificationReceivedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnotificationreceivedeventargs/) | The event data. | ### RefreshConditions Forces the server to refresh all current conditions to synchronize the client with the server.
```csharp public void RefreshConditions() ```
```vbnet Public Sub RefreshConditions() ```
**Exceptions** | Exception | Condition | |---|---| | [InvalidOperationException](https://learn.microsoft.com/dotnet/api/system.invalidoperationexception) | The current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet been created (see [IsCreated](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#iscreated)). | | [OpcException](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcexception/) | Refreshing conditions has failed. For more information see exception details. The following issues can lead to that exception: [BadSubscriptionIdInvalid](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badsubscriptionidinvalid), [BadRefreshInProgress](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badrefreshinprogress) and [BadUserAccessDenied](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#baduseraccessdenied). | **Remarks** The server does not need to be notified about the call to take effect, because of this method directly operates on the server. The client will request a refresh of all condition instances that currenlty are in an interesting state (they have the retain property set to the value true). This includes previous states of a condition instance for which the server maintains branches as well. A client would typically invoke this method when it initially connects to a server and following any situations, such as communication disruptions, in which it would require resynchronization with the server. ### RemoveMonitoredItem 3 overloads | Overload | Description | |---|---| | [RemoveMonitoredItem(OpcMonitoredItem)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#removemonitoreditem-opc-uafx-client-opcmonitoreditem) | Removes the monitored item specified by `item` from the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). | | [RemoveMonitoredItem(IEnumerable<OpcMonitoredItem>)](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#removemonitoreditem-system-collections-generic-ienumerable-of-opc-uafx-client-opcmonitoreditem) | Removes the monitored items specified by `items` from the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). | | [RemoveMonitoredItem(params OpcMonitoredItem\[\])](#removemonitoreditem-opc-uafx-client-opcmonitoreditem-array) | Removes the monitored items specified by `items` from the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). | #### RemoveMonitoredItem(OpcMonitoredItem) Removes the monitored item specified by `item` from the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public void RemoveMonitoredItem(OpcMonitoredItem item) ```
```vbnet Public Sub RemoveMonitoredItem(item As OpcMonitoredItem) ```
**Parameters** | Name | Type | Description | |---|---|---| | `item` | [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) | The [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) to remove. | **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `item` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the orphaned monitored item to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### RemoveMonitoredItem(IEnumerable<OpcMonitoredItem>) Removes the monitored items specified by `items` from the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public void RemoveMonitoredItem(IEnumerable items) ```
```vbnet Public Sub RemoveMonitoredItem(items As IEnumerable(Of OpcMonitoredItem)) ```
**Parameters** | Name | Type | Description | |---|---|---| | `items` | [IEnumerable](https://learn.microsoft.com/dotnet/api/system.collections.generic.ienumerable-1)<[OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/)> | A sequence of [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) instances to remove. | **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `items` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the orphaned monitored items to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. #### RemoveMonitoredItem(params OpcMonitoredItem\[\]) Removes the monitored items specified by `items` from the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) of this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public void RemoveMonitoredItem(params OpcMonitoredItem[] items) ```
```vbnet Public Sub RemoveMonitoredItem(ParamArray items As OpcMonitoredItem()) ```
**Parameters** | Name | Type | Description | |---|---|---| | `items` | params [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/)[] | An array of [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/) instances to remove. | **Exceptions** | Exception | Condition | |---|---| | [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception) | The `items` is a null reference (Nothing in Visual Basic). | **Remarks** The server needs to be notified about the orphaned monitored items to take effect. To do so use the [ApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#applychanges) method. ### ResendData since v2.51 Notifies the server to resend the current values of the [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems) monitoring data changes where the [MonitoringMode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#monitoringmode) is equals to [Reporting](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcmonitoringmode/#reporting).
```csharp public void ResendData() ```
```vbnet Public Sub ResendData() ```
**Exceptions** | Exception | Condition | |---|---| | [InvalidOperationException](https://learn.microsoft.com/dotnet/api/system.invalidoperationexception) | The current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet been created (see [IsCreated](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#iscreated)). | | [OpcException](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcexception/) | The server notification has failed. For more information see exception details. The following issues can lead to that exception: [BadSubscriptionIdInvalid](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badsubscriptionidinvalid) and [BadUserAccessDenied](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#baduseraccessdenied). | ### StartPublishing Enables notifications being send from the server to the client for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public void StartPublishing() ```
```vbnet Public Sub StartPublishing() ```
**Exceptions** | Exception | Condition | |---|---| | [InvalidOperationException](https://learn.microsoft.com/dotnet/api/system.invalidoperationexception) | The current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet been created (see [IsCreated](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#iscreated)). | | [OpcException](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcexception/) | Enabling notifications has failed. For more information see exception details. The following issues can lead to that exception: [BadNothingToDo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badnothingtodo) and [BadTooManyOperations](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badtoomanyoperations). | **Remarks** The server does not need to be notified about the call to take effect, because of this method directly operates on the server. ### StopPublishing Disables notifications being send from the server to the client for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public void StopPublishing() ```
```vbnet Public Sub StopPublishing() ```
**Exceptions** | Exception | Condition | |---|---| | [InvalidOperationException](https://learn.microsoft.com/dotnet/api/system.invalidoperationexception) | The current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet been created (see [IsCreated](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#iscreated)). | | [OpcException](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcexception/) | Disabling notifications has failed. For more information see exception details. The following issues can lead to that exception: [BadNothingToDo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badnothingtodo) and [BadTooManyOperations](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badtoomanyoperations). | **Remarks** The server does not need to be notified about the call to take effect, because of this method directly operates on the server. ### ToString override Returns a string that represents the current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public override string ToString() ```
```vbnet Public Overrides Function ToString() As String ```
**Returns** [String](https://learn.microsoft.com/dotnet/api/system.string) A string that represents the current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) including the used [DisplayName](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#displayname), the [CurrentPublishingIsEnabled](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#currentpublishingisenabled) and the [CurrentPublishingInterval](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#currentpublishinginterval). **Overrides** [ToString()](https://learn.microsoft.com/dotnet/api/system.object.tostring) ### Unsubscribe Deletes this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) and all its [MonitoredItems](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#monitoreditems).
```csharp public void Unsubscribe() ```
```vbnet Public Sub Unsubscribe() ```
**Exceptions** | Exception | Condition | |---|---| | [InvalidOperationException](https://learn.microsoft.com/dotnet/api/system.invalidoperationexception) | The current [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has not yet been created (see [IsCreated](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#iscreated)). | | [OpcException](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcexception/) | Changing the monitoring mode has failed. For more information see exception details. The following issues can lead to that exception: [BadNothingToDo](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badnothingtodo) and [BadTooManyOperations](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badtoomanyoperations). | **Remarks** The server does not need to be notified about the call to take effect, because of this method directly operates on the server. ## Events ### Changed Occurs then a monitored is added, modified, deleted or changes on the [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) were applied.
```csharp public event OpcSubscriptionChangedEventHandler Changed ```
```vbnet Public Event Changed As OpcSubscriptionChangedEventHandler ```
**Event type** [OpcSubscriptionChangedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscriptionchangedeventhandler/) ### DataChangeReceived Occurs then a monitored item receives an event notification which is not handled by an [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) on its [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#datachangereceived) event.
```csharp public event OpcDataChangeReceivedEventHandler DataChangeReceived ```
```vbnet Public Event DataChangeReceived As OpcDataChangeReceivedEventHandler ```
**Event type** [OpcDataChangeReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcdatachangereceivedeventhandler/) **Remarks** This event only occurs if an event notification is not handled by the according [DataChangeReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#datachangereceived) event handler. ### EventReceived Occurs then a monitored item receives an event notification which is not handled by an [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) on its [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#eventreceived) event.
```csharp public event OpcEventReceivedEventHandler EventReceived ```
```vbnet Public Event EventReceived As OpcEventReceivedEventHandler ```
**Event type** [OpcEventReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opceventreceivedeventhandler/) **Remarks** This event only occurs if an event notification is not handled by the according [EventReceived](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcmonitoreditem/members#eventreceived) event handler. ### IsPublishingChanged Occurs then the [IsPublishing](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#ispublishing) property has changed.
```csharp public event EventHandler IsPublishingChanged ```
```vbnet Public Event IsPublishingChanged As EventHandler ```
**Event type** [EventHandler](https://learn.microsoft.com/dotnet/api/system.eventhandler) ### NotificationFailed since v2.57 Occurs then a notification message for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) failed to be received, so that its data changes and events do not reach the monitored items.
```csharp public event OpcNotificationFailedEventHandler NotificationFailed ```
```vbnet Public Event NotificationFailed As OpcNotificationFailedEventHandler ```
**Event type** [OpcNotificationFailedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnotificationfailedeventhandler/) **Remarks** The session requests a failed message again from the server until the server no longer holds it. This event occurs once for each message, however often it fails, and once more with [BadMessageNotAvailable](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcstatuscode/#badmessagenotavailable) when the message is lost. An event which is not handled by this event handler is passed to the [NotificationFailed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/notificationfailed) event of the [OpcClient](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/) which owns this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/). ### NotificationReceived Occurs then a [OpcNotification](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnotification/) for this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/) has been received by the session which owns this [OpcSubscription](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/).
```csharp public event OpcNotificationReceivedEventHandler NotificationReceived ```
```vbnet Public Event NotificationReceived As OpcNotificationReceivedEventHandler ```
**Event type** [OpcNotificationReceivedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnotificationreceivedeventhandler/)