C# Put Dispaly in Sleep Mode

[System.Runtime.InteropServices.DllImport("user32.dll")]
static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, IntPtr wParam, IntPtr lParam);


//OFF
SendMessage(this.Handle, 0x0112, (IntPtr)0xF170, (IntPtr)2);

//ON
 SendMessage(this.Handle, 0x0112, (IntPtr)0xF170, (IntPtr)(-1));