Drag and Drop between Tree controls

Environment: VC6 SP2, NT4 SP5

This article demonstrates drag and drop between tree controls using OLE Drag and Drop. It also allows an item to be dropped on same tree control.When an item is dropped all the children of that item are also dropped on the target. The following key combination can be used:

• Left button, to copy an item
• Ctrl+Left Button,to copy an item
• Shift+Left Button,to move an item

There are two classes :

• CDragDropTreeCtrl, for Tree control. This class also has a helper function AddItem() for adding an item to the tree control.
• CTreeDropTarget, which provides functionality of Drop target

The CDragDropTreeCtrl registers the tree control as the drop target and starts the drag operation in respose to the TVN_BEGINDRAG message.

The CTreeDropTarget is derived from COleDropTarget and serves as drop target. This class overides the following functions:

• OnDragEnter().
• OnDragOver(). This function highlights and expands the item under the mouse pointer and also scrolls the tree control appropriately
• OnDrop(). This function creates the item being dragged in the destination tree control when the user releases the mouse button.

• #include afxole.h in stdafx.h
• Call AfxOleInit() in InitInstance().
• Create an object of CDragDropTreeCtrl in your class.

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