# TreeView<TIdentifier>.DoFoldoutCallback

> Callback signature used to override the TreeView foldout. See TreeView<TIdentifier>.foldoutOverride.

## Definition

* **Type:** Delegate
* **Namespace:** [UnityEditor.IMGUI.Controls](/engine/6000.6/script-reference/unityeditor/imgui/controls.md)
* **Assembly:** UnityEditor.CoreModule

```csharp
public delegate bool TreeView<TIdentifier>.DoFoldoutCallback(Rect position, bool expandedState, GUIStyle style)
```