有很多的软件都实现了自动关机这样的功能。前一阵在Codeproject上看到一个这样的程序，整理了一下共享给大家。里面实现了关机，重启，注销等功能.

using System;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Diagnostics;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;



namespace TimerComputerShutdown
{
/// <summary>
/// Summary description for TimerComputerShutdown.
/// </summary>
public class TimerComputerShutdown : System.Windows.Forms.Form
{
  private System.Windows.Forms.Label labelWhatDoYouWantTheComputerToDo;
  private System.Windows.Forms.ComboBox comboBox;
  private System.Windows.Forms.Label labelSelectDateTimeToShutdownComputer;
  private System.Windows.Forms.DateTimePicker dateTimePicker;
  private System.Windows.Forms.Label labelDateTimeNow;
  private System.Windows.Forms.Label labelDateTimeShutdown;
  private System.Windows.Forms.Label labelNow;
  private System.Windows.Forms.Label labelShutdown;
  private System.Windows.Forms.Panel panelParent;
  private System.Windows.Forms.Panel panelChild;
  private System.Windows.Forms.CheckBox checkBox;
  private System.Windows.Forms.Button buttonCancel;
  private System.Windows.Forms.Button buttonInvoke;
  /// <summary>
  /// Required designer variable.
  /// </summary>
  private System.ComponentModel.Container components = null;
  
  private System.Threading.ThreadStart threadStart;
  private System.Threading.Thread thread;

  [DllImport("user32.dll")] private static extern
   bool SetForegroundWindow(IntPtr hWnd);
  [DllImport("user32.dll")] private static extern
   bool ShowWindowAsync(IntPtr hWnd, int nCmdShow);
  [DllImport("user32.dll")] private static extern
   bool IsIconic(IntPtr hWnd);

  private const int SW_HIDE = 0;
  private const int SW_SHOWNORMAL = 1;
  private const int SW_SHOWMINIMIZED = 2;
  private const int SW_SHOWMAXIMIZED = 3;
  private const int SW_SHOWNOACTIVATE = 4;
  private const int SW_RESTORE = 9;
  private const int SW_SHOWDEFAULT = 10;
  
  public TimerComputerShutdown()
  {
   
   InitializeComponent();

  }

  /// <summary>
  /// Clean up any resources being used.
  /// </summary>
  protected override void Dispose( bool disposing )
  {
   if( disposing )
   {
    if (components != null)
    {
     components.Dispose();
    }
   }
   base.Dispose( disposing )