# HierarchyView.SourceHierarchyChangingEventHandler

> Delegate type used to handle the HierarchyView.SourceHierarchyChanging event.

## Definition

* **Type:** Delegate
* **Namespace:** [Unity.Hierarchy](/engine/6000.7/script-reference/unity/hierarchy.md)
* **Assembly:** UnityEngine.HierarchyModule

```csharp
public delegate void HierarchyView.SourceHierarchyChangingEventHandler(HierarchyView view, Hierarchy oldHierarchy, Hierarchy newHierarchy, HierarchyNodeFlags defaultFlags)
```