利用wmi远程关闭和重启windows主机问题

/// <summary>        /// 获取查询队列        /// </summary>             private static ManagementObjectCollection GetQueryObject(string ip, string username, string password, string queryString)        {            ConnectionOptions co = new ConnectionOptions();            string hostname = !string.IsNullOrEmpty(ip) ? Net.BaseNet.GetRemoteHostName(ip) : "";            co.Username = (string.IsNullOrEmpty(hostname) ? "" : hostname + "\\") + username;            co.Password = password;            ManagementScope scm = string.IsNullOrEmpty(ip) || ip.Trim() == "" || ip.ToLower().Trim() == "localhost" || ip.ToLower().Trim() == "127.0.0.1" ?                new ManagementScope(@"\\localhost\root\cimv2") : new ManagementScope(@"\\" + ip + @"\root\cimv2", co);             ObjectQuery oq = new System.Management.ObjectQuery(queryString);            ManagementObjectSearcher query = new ManagementObjectSearcher(scm, oq);            return query.Get();        }下面就是重启和关机代码:/// <summary>        /// 重?启?计?算?机¨²        /// </summary>        /// <param name="ip">机¨²器¡ÂIP</param>        /// <param name="username">用®?户¡ì名?</param>        /// <param name="password">密¨¹码?</param>        /// <returns></returns>        public static string RebootComputer(string ip, string username, string password)        {            var queryCollection = GetQueryObject(ip, username, password, "SELECT * FROM Win32_OperatingSystem");//获?取¨?远?程¨¬操¨´作Á¡Â             foreach (ManagementObject mo in queryCollection)            {                string[] ss = { "" };                mo.InvokeMethod("Reboot", ss);                return mo.ToString();            }            return "";        }         /// <summary>        /// 关?闭À?计?算?机¨²        /// </summary>        /// <param name="ip">机¨²器¡ÂIP</param>        /// <param name="username">用®?户¡ì名?</param>        /// <param name="password">密¨¹码?</param>        /// <returns></returns>        public static string ShutDownComputer(string ip, string username, string password)        {            var queryCollection = GetQueryObject(ip, username, password, "SELECT * FROM Win32_OperatingSystem");//获?取¨?远?程¨¬操¨´作Á¡Â             foreach (ManagementObject mo in queryCollection)            {                string[] ss = { "" };                mo.InvokeMethod("Win32Shutdown", ss);                return mo.ToString();            }操作win2003,win2008都没问题..就是win7不行....有人知道什么问题不?http://www.jiamaocode.com/Conts/2010/09/17/1261/1261.html            return "";        }