Disable Close button

[jmcilhinney]

I'm not sure if someone else has beaten me to it because I couldn't be bothered searching too hard, but here is a method to disable the Close button in the title bar and the Close option of the system menu of a form. private const int SC_CLOSE = 0xF060;
private const int MF_GRAYED = 0x1;

[DllImport("user32.dll")]
private static extern IntPtr GetSystemMenu(IntPtr hWnd, bool bRevert);

[DllImport("user32.dll")]
private static extern int EnableMenuItem(IntPtr hMenu, int wIDEnableItem, int wEnable);

private void Form1_Load(object sender, System.EventArgs e)
{
EnableMenuItem(GetSystemMenu(this.Handle, false), SC_CLOSE, MF_GRAYED);
}