// 若要允许使用 ASP.NET AJAX 从脚本中调用此 Web 服务，请取消注释以下行。

  [System.Web.Script.Services.ScriptService]

/// <summary>

        /// 需要WebService支持Post调用

        /// </summary>

        public static string PostWebServiceByJson(String URL, String MethodName, Hashtable Pars)

        {

            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(URL + "/" + MethodName);

            request.Method = "POST";

            request.ContentType = "application/json;charset=utf-8";

            request.Credentials = CredentialCache.DefaultCredentials;

            request.Timeout = ;

            byte[] data = Encoding.UTF8.GetBytes(HashtableToJson(Pars));

            request.ContentLength = data.Length;

            Stream writer = request.GetRequestStream();

            writer.Write(data, , data.Length);

            writer.Close();

            StreamReader sr = new StreamReader(request.GetResponse().GetResponseStream(), Encoding.UTF8);

            String retXml = sr.ReadToEnd();

            sr.Close();

            return retXml;

        }

Hashtable ht = new Hashtable();

            ht.Add("LoginName", "Admin");

            ht.Add("Password", "Password");

            ht.Add("AppKey", "");

            HttpHelper.PostWebServiceByJson("http://localhost/OpenApi/MobileService.asmx", "Login", ht);

<webServices>

<protocols>

<add name="HttpGet"/>

<add name="HttpPost"/>

</protocols>

</webServices>