C#中如何对当前窗体进行打印预览

[System.Runtime.InteropServices.DllImport("gdi32.dll")]
public static extern long BitBlt (IntPtr hdcDest, int nXDest, int nYDest, int nWidth, int nHeight, IntPtr hdcSrc, int nXSrc, int nYSrc, int dwRop);
private Bitmap memoryImage;

private void CaptureScreen()
{
   Graphics mygraphics = this.CreateGraphics();
   Size s = this.Size;
   memoryImage = new Bitmap(s.Width, s.Height, mygraphics);
   Graphics memoryGraphics = Graphics.FromImage(memoryImage);
   IntPtr dc1 = mygraphics.GetHdc();
   IntPtr dc2 = memoryGraphics.GetHdc();
   BitBlt(dc2, 0, 0, this.ClientRectangle.Width, this.ClientRectangle.Height, dc1, 0, 0, 13369376);
   mygraphics.ReleaseHdc(dc1);
   memoryGraphics.ReleaseHdc(dc2);
}

private void printDocument1_PrintPage(System.Object sender, System.Drawing.Printing.PrintPageEventArgs e)
{
   e.Graphics.DrawImage(memoryImage, 0, 0);
}

private void printButton_Click(System.Object sender, System.EventArgs e)
{
   CaptureScreen();
   printPreviewDialog1.Show();
}