vc鼠标拖拽效果的实现

                                                           COleDropTarget

1. 主要是COleDropTarget的实现，

注册COleDropTarget对象  BOOL Register( CWnd* pWnd );

2。实现COleDropTargetConstructs a COleDropTarget object.

Operations

RegisterRegisters the window as a valid drop target.RevokeCauses the window to cease being a valid drop target.

Overridables

OnDragEnterCalled when the cursor first enters the window.OnDragLeaveCalled when the cursor is dragged out of the window.OnDragOverCalled repeatedly when the cursor is dragged over the window.OnDragScrollCalled to determine whether the cursor is dragged into the scroll region of the window.OnDropCalled when data is dropped into the window, default handler.OnDropExCalled when data is dropped into the window, initial handler.

3 在派生类中重写