分层表格不显示

Question

我的分层表单出了问题。我用它来显示形状背景模糊的PNG图像。在Windows 7中一切都运行良好，但是当我在Windows XP上运行时，我的表单不会显示。

有我的代码：

public class LayeredForm : Form
{
    public LayeredForm()
    {
        FormBorderStyle = FormBorderStyle.None;
        ShowInTaskbar = false;
        StartPosition = FormStartPosition.Manual;
        Width = 0;
        Height = 0;
        DoubleBuffered = true;
    }

    public void SetBitmap(Bitmap bitmap)
    {
        IntPtr screenDc = Win32Helper.GetDC(IntPtr.Zero);
        IntPtr compatibleMemoryDc = Win32Helper.CreateCompatibleDC(screenDc);
        IntPtr hgdiBitmap = IntPtr.Zero;
        IntPtr hgdiOldBitmap = IntPtr.Zero;

        try
        {
            hgdiBitmap = bitmap.GetHbitmap(Color.FromArgb(0));
            hgdiOldBitmap = Win32Helper.SelectObject(compatibleMemoryDc, hgdiBitmap);
            Win32Helper.SizeStruct size = new Win32Helper.SizeStruct() 
            { 
                X = bitmap.Width,
                Y = bitmap.Height
            };
            Win32Helper.PointStruct sourcePoint = new Win32Helper.PointStruct();
            Win32Helper.PointStruct topPoint = new Win32Helper.PointStruct() 
            { 
                X = Left,
                Y = Top
            };
            Win32Helper.BlendFunctionStruct blend = new Win32Helper.BlendFunctionStruct()
            {
                BlendOp = 255 /* opacity */,
                BlendFlags = 0x00 /* AC_SRC_OVER */,
                AlphaFormat = 0x01 /* AC_SRC_ALPHA */,
                SourceConstantAlpha = byte.MaxValue
            };
            Win32Helper.UpdateLayeredWindow(this.Handle, screenDc, ref topPoint, ref size, compatibleMemoryDc,
                ref sourcePoint, 0, ref blend, 2 /* ULW_ALPHA */);
        }
        finally
        {
            if (screenDc != IntPtr.Zero)
            {
                Win32Helper.ReleaseDC(IntPtr.Zero, screenDc);
            }
            if (hgdiBitmap != IntPtr.Zero)
            {
                Win32Helper.SelectObject(compatibleMemoryDc, hgdiOldBitmap);
                Win32Helper.DeleteObject(hgdiBitmap);
            }
            Win32Helper.DeleteDC(compatibleMemoryDc);
        }
    }

    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams cp = base.CreateParams;
            cp.ExStyle |= 0x00080000;  // Turn on WS_EX_LAYERED
            return cp;
        }
    }
}

我通过扩展使用它，并使用SetBitmap（）函数设置我的图像。我的表单是空的边框，而不是子窗口（WS_EX_LAYERED不适用于旧窗口的子窗口而不是Windows 8）。