关闭显示器

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using System.Diagnostics;


namespace StopWatch
{
    class SYSClass
    {

        public const uint WM_SYSCOMMAND = 0x0112;
        public const uint SC_MONITORPOWER = 0xF170;
        [DllImport("user32")]
        public static extern IntPtr SendMessage(IntPtr hWnd, uint wMsg, uint wParam, int lParam);

        /// <summary>
        /// 关闭显示器 
        /// </summary>
        public void CloseScreen()
        {
            
            IntPtr windowHandle =  Process.GetCurrentProcess().MainWindowHandle;
            SendMessage(windowHandle, WM_SYSCOMMAND, SC_MONITORPOWER, 2);    // 2 为关闭显示器， －1则打开显示器 
        }
    }
}

使用 

new SYSClass().CloseScreen();