# MainToolbarDropdown(MainToolbarContent, Action<Rect>)

> Specify the content and function of a main toolbar dropdown.

## Definition

* **Type:** Constructor
* **Namespace:** [UnityEditor.Toolbars](/engine/6000.6/script-reference/unityeditor/toolbars.md)
* **Assembly:** UnityEditor

```csharp
public MainToolbarDropdown(MainToolbarContent content, Action<Rect> openDropdown)
```

### Parameters

**** (\[MainToolbarContent]\(/engine/6000.6/script-reference/unityeditor/toolbars/maintoolbarcontent)): The visual content for this button.**** (\[Action\<Rect>]\(https\://learn.microsoft.com/dotnet/api/system.action)): The callback that Unity invokes when the user selects the dropdown. Unity provides the `rect` where the dropdown appears as a parameter.