EricBakx has uploaded a patch.
Description:
In our application we use AvalonDock with multiple LayoutDocument content on a LayoutDocumentPane. Our application requires that each LayoutDocument can only exist once on a LayoutDocumentPane. This is the case if a LayoutDocuments Title and the ContentId are identical.
We implemented this feature in AvalonDock as follows.
If a LayoutDocument that already exists on a LayoutDocumentPane is dragged over the LayoutDocumentPane, then the DropTargetInto button is not visible.
So you can't drop the LayoutDocument onto the LayoutDocumentPane.
We have build a dependency property in the DockingManager (AllowDuplicateContent), which is default 'true' and therefore the default behavior is as it was. However, if the user changes the property to 'false', then no duplicate content is allowed and the DropTargetInto button is not visible while dragging a LayoutDocument over the LayoutDocumentPane.
We want to propose this feature to be integrated into AvalonDock, so other users can use it as well.