切换运行系统用户

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
using System.Security.Principal;
using System.Text.RegularExpressions; 

namespace Update
{
    public class ImpersonateHelper
    { 

        [DllImport("advapi32.dll", SetLastError = true)]
        public extern static bool LogonUser(String lpszUsername, String lpszDomain,
         String lpszPassword, int dwLogonType,
         int dwLogonProvider, ref IntPtr phToken); 

        [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
        public extern static bool CloseHandle(IntPtr handle); 

        [DllImport("advapi32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        public extern static bool DuplicateToken(IntPtr ExistingTokenHandle,
         int SECURITY_IMPERSONATION_LEVEL, ref IntPtr DuplicateTokenHandle); 

        public delegate void ImpersonatedWork(); 

        //// <summary>
        /// 以指定用户的身份去做一件事情
        /// </summary>
        /// <param name="UserName"></param>
        /// <param name="PWD"></param>
        /// <param name="WhatToDo"></param>
        public static void ImpersonateAndDo(string UserName, string PWD, ImpersonatedWork WhatToDo)
        {
            string domainName = string.Empty;
            string userName = string.Empty;
            IntPtr tokenHandle = new IntPtr(0);
            IntPtr dupeTokenHandle = new IntPtr(0);
            const int LOGON32_PROVIDER_DEFAULT = 0;
            const int LOGON32_LOGON_INTERACTIVE = 2;
            const int SecurityImpersonation = 2;
            if (!Regex.IsMatch(UserName, @"^\w+[\\]?\w+$"))
            {
                throw new ApplicationException("非法的用户名");
            }
            string[] tmp = UserName.Split(new char[] { '\\' });
            if (tmp.Length > 1)
            {
                domainName = tmp[0];
                userName = tmp[1];
            }
            else
            {
                userName = tmp[0];
            }
            tokenHandle = IntPtr.Zero;
            dupeTokenHandle = IntPtr.Zero;
            bool returnValue = LogonUser(userName, domainName, PWD,
             LOGON32_LOGON_INTERACTIVE, LOGON32_PROVIDER_DEFAULT,
             ref tokenHandle);
            if (!returnValue)
            {
                throw new ApplicationException("取Handle出错了!");
            } 

            //Console.WriteLine("当前用户是: "
            //    + WindowsIdentity.GetCurrent().Name); 

            bool retVal = DuplicateToken(tokenHandle, SecurityImpersonation, ref dupeTokenHandle);
            if (!retVal)
            {
                CloseHandle(tokenHandle);
                throw new ApplicationException("复制Handle出错了!");
            }
            WindowsIdentity newId = new WindowsIdentity(dupeTokenHandle);
            WindowsImpersonationContext impersonatedUser = newId.Impersonate(); 

            if(WhatToDo!=null)
                    WhatToDo(); 

                impersonatedUser.Undo();
                if (tokenHandle != IntPtr.Zero)
                    CloseHandle(tokenHandle);
                if (dupeTokenHandle != IntPtr.Zero)
                    CloseHandle(dupeTokenHandle); 

        } 

    }
}