static BitmapSource GetWindowIcon(IntPtr windowHandle)
        {
            var hIcon = default(IntPtr);

            hIcon = WindowApi.SendMessage(windowHandle, (int)Message.WM_GETICON, WindowApi.ICON_BIG, IntPtr.Zero);

            if (hIcon == IntPtr.Zero)
            {
                hIcon = WindowApi.GetClassLongPtr(windowHandle, WindowApi.GCL_HICON);
            }

            if (hIcon == IntPtr.Zero)
            {
                //TODO: define this constant in the api. it's messy in here.
                hIcon = WindowApi.LoadIcon(IntPtr.Zero, (IntPtr)0x7F00 /*IDI_APPLICATION*/);
            }

            if (hIcon != IntPtr.Zero)
            {
                return(Imaging.CreateBitmapSourceFromHIcon(hIcon, Int32Rect.Empty, BitmapSizeOptions.FromEmptyOptions()));
            }
            else
            {
                throw new InvalidOperationException("Could not load window icon.");
            }
        }