The framework calls this member function when the user releases the left mouse button over a window that has registered itself as the recipient of dropped files.
A pointer to an internal data structure that describes the dropped files. This handle is used by the DragFinish, DragQueryFile, and DragQueryPoint Windows functions to retrieve information about the dropped files.
Typically, a derived class will be designed to support dropped files and it will register itself during window construction.
This member function is called by the framework to allow your application to handle a Windows message. The parameters passed to your function reflect the parameters received by the framework when the message was received. If you call the base-class implementation of this function, that implementation will use the parameters originally passed with the message and not the parameters you supply to the function.