using System.Runtime.InteropServices;

private const int SC_CLOSE = 0xF060;

private const int MF_ENABLED = 0x00000000;

private const int MF_GRAYED = 0x00000001;

private const int MF_DISABLED = 0x00000002;



[DllImport("user32.dll", EntryPoint = "GetSystemMenu")]

private static extern IntPtr GetSystemMenu(IntPtr hWnd, int bRevert);

[DllImport("User32.dll")]

public static extern bool EnableMenuItem(IntPtr hMenu, int uIDEnableItem, int uEnable);

protected override CreateParams CreateParams

{
get
   {
const int CS_NOCLOSE = 0x200;
      CreateParams cp = base.CreateParams;
      cp.ClassStyle = cp.ClassStyle | CS_NOCLOSE;
return cp;
   }

}