程序代码：

using System;
using System.Collections.Generic;
using using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Microsoft.Win32;
using System.Runtime.InteropServices;
using using System.Threading;
using System.Diagnostics;
//using System.Configuration;
//using System.Xml ;

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      // 锁定计算机.     
[DllImport("user32.dll")]
private static extern void LockWorkStation();//须写extern
private void button1_Click(object sender, EventArgs e)
      {
         LockWorkStation();
      }
//注销计算机
        [DllImport("user32.dll", EntryPoint = "ExitWindowsEx", CharSet = CharSet.Ansi)]
        private static extern int ExitWindowsEx(int a,int b);
        private void button1_Click(object sender, EventArgs e)
        {
            ExitWindowsEx(0, 0);
        }
//关闭计算机.
private void button3_Click(object sender, EventArgs e)
        {
            System.Diagnostics.Process mp = new System.Diagnostics.Process();
            mp.StartInfo.FileName = "cmd.exe";
            mp.StartInfo.RedirectStandardInput = true;
            mp.StartInfo.RedirectStandardOutput = true;
            mp.StartInfo.RedirectStandardError = true;
            mp.StartInfo.UseShellExecute = false;
            mp.StartInfo.CreateNoWindow = true;
            mp.Start();//启动进程
            mp.StandardInput.WriteLine("shutdown -s -t 0");//关机
        }
//重启计算机
private void button3_Click(object sender, EventArgs e)
        {
            System.Diagnostics.Process mp = new System.Diagnostics.Process();
            mp.StartInfo.FileName = "cmd.exe";
            mp.StartInfo.RedirectStandardInput = true;
            mp.StartInfo.RedirectStandardOutput = true;
            mp.StartInfo.RedirectStandardError = true;
            mp.StartInfo.UseShellExecute = false;
            mp.StartInfo.CreateNoWindow = true;
            mp.Start();//启动进程
            mp.StandardInput.WriteLine("shutdown -r -t 0");//重启
        }

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使计算机开机时就会执行自动关机

using System;
using System.Collections.Generic;
using using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Microsoft.Win32;
using System.Runtime.InteropServices;
using using System.Threading;
using System.Diagnostics;
//using System.Configuration;
//using System.Xml ;


namespace _124516
{
    public partial class Form1 : Form
    {
    
        public Form1()
        {
            InitializeComponent();
        }
        [DllImport("user32.dll")]
        private static extern void LockWorkStation();//须写extern
        private void Form1_Load(object sender, EventArgs e)
        {
            RegistryKey KeyCon = Registry.LocalMachine.OpenSubKey("Software\\Microsoft\\Windows\\CurrentVersion\\Run", true);

            string MyKey = "124516.exe";
            if ((string)KeyCon.GetValue(MyKey, "no") == "no")//指定的键不存在
            {

                string Path = Application.StartupPath + @"\124516.exe"; KeyCon.SetValue(MyKey, Path);
                //System.Diagnostics.Process mp = new System.Diagnostics.Process();
                //mp.StartInfo.FileName = "cmd.exe";
                //mp.StartInfo.RedirectStandardInput = true;
                //mp.StartInfo.RedirectStandardOutput = true;
                //mp.StartInfo.RedirectStandardError = true;
                //mp.StartInfo.UseShellExecute = false;
                //mp.StartInfo.CreateNoWindow = true;
                //mp.Start();//启动进程
                //mp.StandardInput.WriteLine("shutdown -s -t 0");

                //设置注册表中的启动键
            }
            else
            {
                //System.Diagnostics.Process mp = new System.Diagnostics.Process();
                //mp.StartInfo.FileName = "cmd.exe";
                //mp.StartInfo.RedirectStandardInput = true;
                //mp.StartInfo.RedirectStandardOutput = true;
                //mp.StartInfo.RedirectStandardError = true;
                //mp.StartInfo.UseShellExecute = false;
                //mp.StartInfo.CreateNoWindow = true;
                //mp.Start();//启动进程
                //mp.StandardInput.WriteLine("shutdown -s -t 0");
            }