# Read and write values

<dl class="api-definition">
<dt>Concept</dt>
<dd><a href="/docs/development/opcua/server/read-write-values">Read and write values</a></dd>
</dl>

| Type | Description |
|---|---|
| [OpcAttribute](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/) | Identifies the different attributes which define the characteristics and additional metadata of a node. |
| [OpcAttributeValue&lt;T&gt;](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattributevalue-1/) | Represents the immutable value of an attribute. |
| [OpcDataVariableNode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcdatavariablenode/) | Provides a node to represent complex data structures expose their information as complex data types, as well as components in the address space. |
| [OpcMonitoredItem](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcmonitoreditem/) | Provides information about a node and its attribute being monitored by a dedicated [OpcSession](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcsession/). |
| [OpcMonitoredItemEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcmonitoreditemeventargs/) | Provides the event data for the [MonitoredItemCreated](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#monitoreditemcreated), [MonitoredItemDeleted](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#monitoreditemdeleted) and [MonitoredItemModified](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#monitoreditemmodified) event. |
| [OpcNodeAccessEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodeaccesseventargs/) | Provides the event data for the events [BeforeRead](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#beforeread), [AfterRead](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#afterread), [BeforeWrite](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#beforewrite) and [AfterWrite](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#afterwrite). |
| [OpcNodeAccessToken](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodeaccesstoken/) | Represents the access to one attribute of a node of an [OpcNodeManager](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/) requested by a read or write operation of a client (see [Read](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#read) and [Write](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/members#write)). |
| [OpcNodeManager](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcnodemanager/) | Provides an abstract base class used to organize and maintain the address space or only a part of it. |
| [OpcReadAttributeValueCallback&lt;T&gt;](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcreadattributevaluecallback-1/) | Represents the method that will read the value of a node attribute. |
| [OpcReadAttributeValueContext](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcreadattributevaluecontext/) | Provides node sensitive information and services about the system which belong to the current situation (process, thread, session, node, etc.) used for reading the value of a node attribute. |
| [OpcReadVariableValueCallback](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcreadvariablevaluecallback/) | Represents the method that will read the value of a variable node. |
| [OpcReadVariableValueContext](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcreadvariablevaluecontext/) | Provides variable node sensitive information and services about the system which belong to the current situation (process, thread, session, variable node, etc.) used for reading the value of a variable node. |
| [OpcResult](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcresult/) | Provides information indicating and describing the outcome of an operation. |
| [OpcServer](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcserver/) | Represents an OPC UA server which provides the address space defined by its [NodeManagers](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.server.opcserver/members#nodemanagers) to its clients. |
| [OpcText](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opctext/) | Represents a human readable [string](https://learn.microsoft.com/dotnet/api/system.string) value optionally associated with a [Culture](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opctext/members#culture) and localization relevant information. |
| [OpcVariableNode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcvariablenode/) | Defines a node to use to represent values which may be simple or complex. |
| [OpcVariableValue&lt;T&gt;](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcvariablevalue-1/) | Represents the immutable value of a variable. |
| [OpcWriteAttributeValueCallback&lt;T&gt;](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcwriteattributevaluecallback-1/) | Represents the method that will write the value of a node attribute. |
| [OpcWriteAttributeValueContext](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcwriteattributevaluecontext/) | Provides node sensitive information and services about the system which belong to the current situation (process, thread, session, node, etc.) used for writing the value of a node attribute. |
| [OpcWriteVariableValueCallback](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcwritevariablevaluecallback/) | Represents the method that will write the value of a variable node. |
| [OpcWriteVariableValueContext](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcwritevariablevaluecontext/) | Provides variable node sensitive information and services about the system which belong to the current situation (process, thread, session, variable node, etc.) used for writing the value of a variable node. |