C#代码实现HTTP请求并获取远程资源字符串

#region 执行请求的连接,获取远程资源,返回String
        ///   <summary>
        ///   执行请求的连接,获取远程资源,返回String
        ///   </summary>
        /// <create>zhangjj</create>
        /// <createTime>2007-12-27</createTime>
        ///   <param   name="url"> 远程资源连接URL </param>
        ///   <param   name="encode"> 编码格式（Default   =   ""） "utf-8"  "gb2132" </param>
        ///   <returns> 返回获取的字符串 </returns>
        public static string HttpWebResponseString(string url, string encode)
        {
            string str = "";
            try
            {
                HttpWebRequest httpRequest = (HttpWebRequest)WebRequest.Create(url);
                httpRequest.UserAgent = @"Mozilla/4.0   (compatible;   MSIE   6.0;   Windows   NT   5.1;   SV1;   .NET   CLR   2.0.40607;   .NET   CLR   1.1.4322)";
                HttpWebResponse httpResponse = (HttpWebResponse)httpRequest.GetResponse();
                if (httpRequest.HaveResponse)
                {
                    StreamReader sr;
                    if (encode != null && encode != "")
                    {
                        sr = new StreamReader(httpResponse.GetResponseStream(), Encoding.GetEncoding(encode));
                    }
                    else
                    {
                        sr = new StreamReader(httpResponse.GetResponseStream(), Encoding.Default);
                    }
                    str = sr.ReadToEnd();
                    sr.Close();