using System.Runtime.InteropServices;//引用,放在哪不用说了吧....
[DllImport("dwmapi.dll")]
public static extern int DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS pMarinset);
[StructLayout(LayoutKind.Sequential)]
public struct MARGINS
{
  public int Right;
  public int left;
  public int Top;
  public int Bottom;
}
private void Form1_Load(object sender, EventArgs e)
{
  this.BackgroundImage = null;
  MARGINS margins = new MARGINS();
  margins.left = -1;
  margins.Right = -1;
  margins.Top = -1;
  margins.Bottom = -1;
  IntPtr hwnd = Handle;
  int result = DwmExtendFrameIntoClientArea(hwnd, ref margins);
  this.BackColor = Color.Black;
  this.label1.Text = "。。。";
  this.label1.BackColor = Color.Transparent;
  this.label1.ForeColor = Color.White;
}