开始拖放操作时保留前景窗口

In my .Net application, the user can drag rows from a grid on a main window into other application windows. Often the main application window is behind the window that the user is dragging into. By default, as soon as the mouse button is depressed on the main window, it gains focus, hiding the window that the user wants to drag onto.In my .Net application, the user can drag rows