# EventCallback<TEventType, TCallbackArgs>

> Defines the structure of a callback that can be registered onto an element for an event type, along with a custom user defined argument.

## Definition

* **Type:** Delegate
* **Namespace:** [UnityEngine.UIElements](/engine/6000.7/script-reference/unityengine/uielements.md)
* **Assembly:** UnityEngine.UIElementsModule

```csharp
public delegate void EventCallback<in TEventType, in TCallbackArgs>(TEventType evt, TCallbackArgs userArgs)
```