class Program

    {

        static void Main(string[] args)

        {

            var m = "m=" + JsonConvert.SerializeObject(new { age = , name = "jxp" });

            var a = HttpHelper.PostRequest("http://localhost:7132/Jxp.asmx/HelloWorld", DataTypeEnum.Form, m);

            var xmldoc = new XmlDocument();

            xmldoc.LoadXml(a);

            var nsMgr = new XmlNamespaceManager(xmldoc.NameTable); nsMgr.AddNamespace("ns", "http://tempuri.org/");

            XmlNode errorNode = xmldoc.SelectSingleNode("/ns:string", nsMgr);

            var b = JsonConvert.DeserializeObject(errorNode.InnerText);

            Console.WriteLine(b);

            Console.ReadKey();

        }

    }

[WebMethod]

public string HelloWorld(string m)

{

      return m;

}

public class HttpHelper

    {

        /// <summary>

        /// Post带参请求

        /// </summary>

        /// <param name="url"></param>

        /// <param name="contentType">指定参数类型</param>

        /// <param name="strData"></param>

        /// <param name="dicHeader"></param>

        /// <returns></returns>

        public static string PostRequest(string url, DataTypeEnum contentType, string strData, Dictionary<string, string> dicHeader = null)

        {

            string result;

            var webRequest = WebRequest.Create(url);

            if (dicHeader != null)

                foreach (var m in dicHeader)

                {

                    webRequest.Headers.Add(m.Key, m.Value);

                }

            webRequest.Method = MethodTypeEnum.Post.ToString();

            webRequest.Proxy = null;

            if (contentType == DataTypeEnum.Form)

            {

                webRequest.ContentType = "application/x-www-form-urlencoded";

            }

            else

            {

                webRequest.ContentType = "application/" + contentType;

            }

            byte[] reqBodyBytes = System.Text.Encoding.UTF8.GetBytes(strData);

            Stream reqStream = webRequest.GetRequestStream();//加入需要发送的参数

            reqStream.Write(reqBodyBytes, , reqBodyBytes.Length);

            reqStream.Close();

            using (var reader = new StreamReader(webRequest.GetResponse().GetResponseStream()))

            {

                result = reader.ReadToEnd();

            }

            return result;

        }

        /// <summary>

        /// Get不带参请求

        /// </summary>

        /// <param name="url"></param>

        /// <returns></returns>

        public static string GetRequest(string url)

        {

            string result;

            WebRequest webRequest = WebRequest.Create(url);

            webRequest.Method = MethodTypeEnum.Get.ToString();

            webRequest.Proxy = null;

            using (var reader = new StreamReader(webRequest.GetResponse().GetResponseStream()))

            {

                result = reader.ReadToEnd();

            }

            return result;

        }

    }

    /// <summary>

    /// 带参数据类型

    /// </summary>

    public enum DataTypeEnum

    {

        Json,

        Xml,

        Form

    }

    /// <summary>

    /// 带参数据类型

    /// </summary>

    public enum MethodTypeEnum

    {

        Get,

        Post

    }