# API Changes in v2.57

> Reference: API changes of Opc.UaFx.Advanced in v2.57: 8 added, 0 removed, 0 changed, 0 obsoleted.

<dl class="api-definition">
<dt>Releases</dt>
<dd>v2.57.0, v2.57.1</dd>
<dt>Compared with</dt>
<dd>v2.56.0</dd>
<dt>Package</dt>
<dd>Opc.UaFx.Advanced</dd>
</dl>

## Added

### Opc.UaFx

| Symbol | Signature |
|---|---|
| [OpcAttribute.DataTypeDefinition](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcattribute/#datatypedefinition) | `DataTypeDefinition = 23` |

### Opc.UaFx.Client

| Symbol | Signature |
|---|---|
| [OpcClient.NotificationFailed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/notificationfailed) | `public event OpcNotificationFailedEventHandler NotificationFailed` |
| [OpcClient.OnNotificationFailed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcclient/onnotificationfailed) | `protected virtual void OnNotificationFailed(OpcNotificationFailedEventArgs e)` |
| [OpcNotificationFailedEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnotificationfailedeventargs/)<span class="api-meta">3 members</span> | `public class OpcNotificationFailedEventArgs : EventArgs` |
| [OpcNotificationFailedEventHandler](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcnotificationfailedeventhandler/) | `public delegate void OpcNotificationFailedEventHandler(object sender, OpcNotificationFailedEventArgs e)` |
| [OpcSubscription.NotificationFailed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#notificationfailed) | `public event OpcNotificationFailedEventHandler NotificationFailed` |
| [OpcSubscription.OnNotificationFailed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscription/members#onnotificationfailed) | `protected virtual void OnNotificationFailed(OpcNotificationFailedEventArgs e)` |
| [OpcSubscriptionSetup.NotificationFailed](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.client.opcsubscriptionsetup/members#notificationfailed) | `public OpcNotificationFailedEventHandler NotificationFailed { get; set; }` |