This function returns NULL when called for an MDI main frame wIndow (CMDIFrameWnd). In an MDI application, the MDI main frame wIndow does not have a view associated with it. Instead, each individual child wIndow (CMDIChildWnd) has one or more associated views. The active view in an MDI application can be obtained by first finding the active MDI child wIndow and then finding the active view for that child wIndow.
