protected SubclassingWindow(IntPtr subclassId, IntPtr hWnd)
 {
     _subclassId = subclassId;
     Hwnd        = hWnd;
     _wndProc    = SubClassProc;
     AssignHandle();
 }
 private static extern int RemoveWindowSubclass(IntPtr hWnd, SubClassCallback newProc, IntPtr uIdSubclass);
 private static extern int SetWindowSubclass(IntPtr hWnd, SubClassCallback newProc, IntPtr uIdSubclass, IntPtr dwRefData);