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If you set a background picture for a Winform and add some transparent control on the form. All controls on the form will displayed one by one. The winform displays in very slow speed. I browsed some article and found the solution. Add the following code to override the BackgroundImage property of the winform.

    private Bitmap m_BackgroundBitmap;
    private const int SCREEN_WIDTH = 1024;
    private const int SCREEN_HEIGHT = 768;
    public override Image BackgroundImage
    {
      set
      {
        m_BackgroundBitmap = new Bitmap(SCREEN_WIDTH,SCREEN_HEIGHT,PixelFormat.Format32bppPArgb);
        Graphics g = Graphics.FromImage(m_BackgroundBitmap);
        g.DrawImage(value, 0, 0, m_BackgroundBitmap.Width, m_BackgroundBitmap.Height);
        g.Dispose();
      }

      get
      {
        return m_BackgroundBitmap;
      }
    }

Compile and test the application. Everything is OK. There are an useful article from MSDN which talks about the performance of the Windows Form application. The Figure 5 give the sample code to resolve the problem for the transparent background winform.

Technorati : C#