---
title: RegisterReferenceUnloadedCallback(Action<T>)
product: Unity Editor
version: '7000.0'
latest_version: '7000.0'
status: This page documents version 7000.0. The latest version is 7000.0.
canonical: https://docs.unity.com/en-us/engine/7000.0/script-reference/unityengine/uielements/visualelementreference1/registerreferenceunloadedcallback
latest_url: https://docs.unity.com/en-us/engine/7000.0/script-reference/unityengine/uielements/visualelementreference1/registerreferenceunloadedcallback.md
last_updated: 2026-10-07
generated_at: 2026-11-11T11:53:52.084Z
locale: en-us
---

# RegisterReferenceUnloadedCallback(Action<T>)

> Registers a callback for when the referenced object is unloaded. This occurs when the document is destroyed, such as when a live reload occurs after the VisualTreeAsset changes. At this point, all references are invalid and should be cleared.

## Definition

* **Type:** Method
* **Namespace:** [UnityEngine.UIElements](/engine/7000.0/script-reference/unityengine/uielements.md)
* **Assembly:** UnityEngine.UIElementsModule

```csharp
public void RegisterReferenceUnloadedCallback(Action<T> callback)
```

### Parameters

**** (\[Action\<T>]\(https\://learn.microsoft.com/dotnet/api/system.action-1)): The callback to invoke when the reference is unloaded.