public static string PostDataToUrl(string url, System.Text.Encoding encoding, System.Collections.Specialized.NameValueCollection data)
        {
            //设置HttpWebRequest
            System.Net.HttpWebRequest request = (System.Net.HttpWebRequest)System.Net.HttpWebRequest.Create(new Uri(url));
            request.UserAgent = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; .NET CLR 1.1.4322; .NET CLR 2.0.50727)";
            request.ContentType = "application/x-www-form-urlencoded";
            request.Method = "POST";
            request.KeepAlive = false;

            byte[] buffer;
            using (System.IO.MemoryStream ms = new System.IO.MemoryStream())
            {
                for (int i = 0; i < data.Count; i++)
                {
                    buffer = encoding.GetBytes(data.Keys[i]);
                    if (i > 0)
                        ms.WriteByte(Convert.ToByte('&'));
                    ms.Write(buffer, 0, buffer.Length);
                    ms.WriteByte(Convert.ToByte('='));
                    buffer = encoding.GetBytes(HttpUtility.UrlEncode(data[i]));
                    ms.Write(buffer, 0, buffer.Length);
                }
                buffer = ms.ToArray();
            }

            request.ContentLength = buffer.Length;
            using (System.IO.Stream requestStream = request.GetRequestStream())
            {
                requestStream.Write(buffer, 0, buffer.Length);
                requestStream.Close();
            }

            try
            {
                //获取数据
                using (System.Net.HttpWebResponse response = (System.Net.HttpWebResponse)(request.GetResponse()))
                using (System.IO.Stream stream = response.GetResponseStream())
                using (System.IO.StreamReader reader = new System.IO.StreamReader(stream, encoding))
                {
                    string result = reader.ReadToEnd();
                    reader.Close();
                    stream.Close();
                    response.Close();
                    return result;
                }
            }
            finally
            {
                request.Abort();
            }
        }

data是方法传的值。。。。

 private void BindApplist(int pageindex)
        {
            NameValueCollection param = new NameValueCollection();
            param.Add("action", "8");
            param.Add("pageindex", pageindex+"");
            param.Add("pagesize", AspNetPager1.PageSize+"");
            param.Add("cateid", Request.QueryString["cateid"]);
            param.Add("boardsid", Request.QueryString["boardsid"]);
       
            string result = WebUtils.PostDataToUrl(_interfaceUrl, Encoding.UTF8, param);
            if (!string.IsNullOrEmpty(result))
            {
                result = StringHelper.ConvertUnicode2Chinese(result);
                JObject obj = (JObject)JsonConvert.DeserializeObject(result);
                var state = TypeHelper.TryParse(obj["state"].ToString(), -1);
                if (state == 0)
                {
                    JArray jar = (JArray)obj["data"];
                    this.AspNetPager1.RecordCount = TotalCount();
                    lstApps.DataSource = jar;
                    lstApps.DataBind();
                }
            }
        }

调试到buffer = encoding.GetBytes(HttpUtility.UrlEncode(data[i]));就报错了。。。。。。