# RegisterReferenceResolvedCallback(Action<VisualElement>)

> Registers a callback for when the reference is resolved from the document. When you register a callback, if the reference is already resolved, the callback is immediately invoked.

## Definition

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

```csharp
public void RegisterReferenceResolvedCallback(Action<VisualElement> callback)
```

### Parameters

**** (\[Action\<VisualElement>]\(https\://learn.microsoft.com/dotnet/api/system.action)): The callback to invoke when the reference is resolved.