public static extern int SendMessage(IntPtr hWnd, W32_HDM msg, int wParam, ref RECT rect);
public static extern int SendMessage(IntPtr hWnd, W32_HDM msg, int wParam, IntPtr lParam);
public static extern int SendMessage(IntPtr hWnd, W32_HDM msg, int wParam, ref HDITEM hditem);
internal static extern int SendMessage( IntPtr hWnd, W32_HDM msg, int wParam, int lParam );