# EventArg

> Base class for all instances of EventArg<TArg>.

## Definition

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

```csharp
public abstract class EventArg
```

## Remarks

Use the [EventArg.Create](/engine/6000.7/script-reference/unityengine/uielements/eventarg/create.md) factory method to create instances and [EventArg\<TArg>.Register](/engine/6000.7/script-reference/unityengine/uielements/eventarg1/register.md), [EventArg\<TArg>.Unregister](/engine/6000.7/script-reference/unityengine/uielements/eventarg1/unregister.md) to assign argument values to individual elements for all callbacks that use this argument identifier in their definition.

Additional Resources: [EventArg\<TArg>](/engine/6000.7/script-reference/unityengine/uielements/eventarg1.md), [EventCallbackDefinition](/engine/6000.7/script-reference/unityengine/uielements/eventcallbackdefinition.md)

## Static Methods

| Method                                                                              | Description                                                                                                                      |
| ----------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------- |
| [Create](/engine/6000.7/script-reference/unityengine/uielements/eventarg/create.md) | Creates a [EventArg\<TArg>](/engine/6000.7/script-reference/unityengine/uielements/eventarg1.md) containing a unique identifier. |