调用NtShutDownSystem失败，求助啊！

Question

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Runtime.InteropServices;namespace CSharp瞬间关机
{
    public partial class Form1 : Form
    {
        [DllImport("advapi32.dll")]
         public static extern bool OpenProcessToken(IntPtr ProcessHandle, int access, ref IntPtr TokenHandle);            [DllImport("advapi32.dll")]
            public static extern bool AdjustTokenPrivileges(IntPtr TokenHandle, bool Disable, ref TokenLuid NewState, int BufferLength, IntPtr PreviousState,IntPtr ReturnLength);
           
            public struct TokenLuid
            { public int Count;
            public long Luid;
            public int attr;
            }
          [DllImport("advapi32.dll")]
            public static extern  bool LookupPrivilegeValue(string lps,string lpn,ref long lpLuid);          public const int SE_PRIVILEGE_ENABLED = 0x00000002;
          public const int TOKEN_QUERY = 0x00000008;
          public const int TOKEN_ADJUST_PRIVILEGES = 0x00000020;
          public string SE_SHUTDOWN_NAME = "SeShutdownPrivilege";          
           [DllImport("kernel32.dll")]
           public static extern IntPtr GetCurrentProcess();           //Declare Function NtShutdownSystem& Lib "ntdll" (ByVal ShutdownAction As Int32)           [DllImport("ntdll.dll")]
          private static extern void NtShutdownSystem(int ShutdownAction);
            const int SHUTDOWN = 0;
            const int POWEROFF = 2;  public Form1()
        {
            InitializeComponent();
        }        private void Form1_Load(object sender, EventArgs e)
        {
            IntPtr a =IntPtr.Zero;
            IntPtr b = GetCurrentProcess();
            
            TokenLuid d;
            d.Count=1;
            d.Luid=0;
            d.attr=SE_PRIVILEGE_ENABLED;           OpenProcessToken(b, TOKEN_QUERY | TOKEN_ADJUST_PRIVILEGES, ref a);
            LookupPrivilegeValue(null,SE_SHUTDOWN_NAME, ref d.Luid);
            AdjustTokenPrivileges(a, false, ref d, 0, IntPtr.Zero, IntPtr.Zero);
                        }        private void button1_Click(object sender, EventArgs e)
        {
            NtShutdownSystem(2);
            
        }        
    }
}
为什么失败呢...