# OpcNodeChangesEventHandler Delegate

> Reference: Represents the method that will handle BeforeApplyChanges, AfterApplyChanges and ChangesUnhandled events.

<span class="api-meta">since v2.10</span>

<dl class="api-definition">
<dt>Namespace</dt>
<dd><a href="../namespaces/opc.uafx">Opc.UaFx</a></dd>
<dt>Assembly</dt>
<dd>Opc.UaFx.Advanced.dll</dd>
<dt>Package</dt>
<dd>Opc.UaFx.Advanced v2.59.0</dd>
</dl>

Represents the method that will handle [BeforeApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnode/members#beforeapplychanges), [AfterApplyChanges](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnode/members#afterapplychanges) and [ChangesUnhandled](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnode/members#changesunhandled) events.

## Syntax

<div class="api-signature" data-lang="csharp">

```csharp
public delegate void OpcNodeChangesEventHandler(
    object sender,
    OpcNodeChangesEventArgs e)
```

</div>

<div class="api-signature" data-lang="vbnet">

```vbnet
Public Delegate Sub OpcNodeChangesEventHandler(
    sender As Object,
    e As OpcNodeChangesEventArgs)
```

</div>

## Parameters

| Name | Type | Description |
|---|---|---|
| `sender` | [Object](https://learn.microsoft.com/dotnet/api/system.object) | The source of the event (typically an instance of the [OpcNode](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnode/) class). |
| `e` | [OpcNodeChangesEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodechangeseventargs/) | An instance of the [OpcNodeChangesEventArgs](https://www.traeger.de/en/docs/development/opcua/api/v2.59/opc.uafx.opcnodechangeseventargs/) class containing the event data. |

## Applies to

| Package | Versions |
|---|---|
| Opc.UaFx.Advanced | v2.10–v2.59 |