监测远程登录（会话）的问题（WTSEnumerateSessions（）） 请教高手

我想用WTSEnumerateSessions（）函数枚举会话，就如同net session命令和[共享文件夹－会话]功能一样。但是只能枚举出一个本机的，不能枚举出其它远程用户的，这是为什么呢？

我是vs2008 c# winxp环境。

附程序
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

//using System.Management;
using System.Runtime;
using System.Runtime.InteropServices;

namespace AutoLogOffSession
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
TSControl.WTS_SESSION_INFO[] pSessionInfo = TSControl.SessionEnumeration();

for (int i = 0; i < pSessionInfo.Length; i++)
{
//if (pSessionInfo[i].SessionID != 0)
{
try
{
int count = 0;
IntPtr buffer = IntPtr.Zero;
StringBuilder sb = new StringBuilder();
bool bsuccess = TSControl.WTSQuerySessionInformation(IntPtr.Zero, pSessionInfo[i].SessionID, TSControl.WTSInfoClass.WTSUserName, out sb, out count);
if (bsuccess)
{
MessageBox.Show(sb.ToString());
}
bsuccess = TSControl.WTSQuerySessionInformation(IntPtr.Zero, pSessionInfo[i].SessionID, TSControl.WTSInfoClass.WTSConnectState, out sb, out count);
if (bsuccess)
{
MessageBox.Show(sb.ToString());
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
}
}
}
public class TSControl
{
[DllImport("wtsapi32", CharSet = CharSet.Auto, SetLastError = true)]
private static extern bool WTSEnumerateSessions(int hServer, int Reserved, int Version, ref long ppSessionInfo, ref int pCount);

[DllImport("wtsapi32.dll")]
public static extern void WTSFreeMemory(System.IntPtr pMemory);

[DllImport("wtsapi32.dll")]
public static extern bool WTSLogoffSession(int hServer, long SessionId, bool bWait);
[DllImport("Wtsapi32.dll")]
public static extern bool WTSQuerySessionInformation(
System.IntPtr hServer, int sessionId, WTSInfoClass wtsInfoClass, out StringBuilder ppBuffer, out int pBytesReturned);

public enum WTSInfoClass
{
WTSInitialProgram,
WTSApplicationName,
WTSWorkingDirectory,
WTSOEMId,
WTSSessionId,
WTSUserName,
WTSWinStationName,
WTSDomainName,
WTSConnectState,
WTSClientBuildNumber,
WTSClientName,
WTSClientDirectory,
WTSClientProductId,
WTSClientHardwareId,
WTSClientAddress,
WTSClientDisplay,
WTSClientProtocolType
}

public enum WTS_CONNECTSTATE_CLASS
{
WTSActive,
WTSConnected,
WTSConnectQuery,
WTSShadow,
WTSDisconnected,
WTSIdle,
WTSListen,
WTSReset,
WTSDown,
WTSInit,
}

public struct WTS_SESSION_INFO
{
public int SessionID;
[MarshalAs(UnmanagedType.LPTStr)]
public string pWinStationName;
public WTS_CONNECTSTATE_CLASS state;
}

public static WTS_SESSION_INFO[] SessionEnumeration()
{
//Set handle of terminal server as the current terminal server
int hServer = 0;
bool RetVal;
long lpBuffer = 0;
int Count = 0;
long p;
WTS_SESSION_INFO Session_Info = new WTS_SESSION_INFO();
WTS_SESSION_INFO[] arrSessionInfo;
RetVal = WTSEnumerateSessions(hServer, 0, 1, ref lpBuffer, ref Count);
arrSessionInfo = new WTS_SESSION_INFO[0];
if (RetVal)
{
arrSessionInfo = new WTS_SESSION_INFO[Count];
int i;
p = lpBuffer;
for (i = 0; i < Count; i++)
{
arrSessionInfo[i] = (WTS_SESSION_INFO)Marshal.PtrToStructure(new IntPtr(p), Session_Info.GetType());
p += Marshal.SizeOf(Session_Info.GetType());
}
WTSFreeMemory(new IntPtr(lpBuffer));
}
else
{
//Insert Error Reaction Here
}
return arrSessionInfo;
}
}
}