ServiceHelper

    public class ServiceHelper
    {
        private static string _baseUrl = $@"http://{Config.Instance.MesServerUrl}/";
        private static string _sessionHeader;
        public static void ClearSession()
        {
            _sessionHeader = "";
        }
        public static string SessionId;

        public static string BaseUrl
        {
            get { return _baseUrl; }
            set { _baseUrl = $@"http://{value}/";} //value  包含IP和端口号 + 后台服务名， 如:localhost:8080/DadeMes
        } 


        /// <summary>
        /// HttpClient实现Get请求
        /// <param name="subUrl">子URL前面必须带 "/" 符号</param>
        /// </summary>
        public static string Get(string subUrl)
        {
            try
            {
                using (var client = GetClient())
                {
                    return client.DownloadString(subUrl);

                }
            }
            catch (WebException)
            {
                throw new Exception("无法连接服务器");
            }
        }

        /// <summary>
        /// Post
        /// </summary>
        /// <param name="url">子地址</param>
        /// <param name="strData">要传输的json字符串</param>
        /// <returns></returns>
        public static string Post(string url, string strData = "")
        {
            try
            {
                using (var client = GetClient())
                {
                    var postData = Encoding.UTF8.GetBytes(strData); //编码，尤其是汉字，事先要看下抓取网页的编码方式
                    var responseData = client.UploadData(url, "POST", postData); //得到返回字符流
                    if (string.IsNullOrWhiteSpace(_sessionHeader))
                    {
                        _sessionHeader = client.ResponseHeaders["Set-Cookie"];//保存session
                    }
                    return Encoding.UTF8.GetString(responseData); //解码
                }
            }
            catch (WebException ex)
            {
                throw new Exception("无法连接服务器");
            }
        }

        /// <summary>
        /// 将本地文件上传到服务器
        /// </summary>
        /// <param name="url">服务器路径</param>
        /// <param name="filePath">本地路径</param>
        /// <returns>上传成功后返回的是上文件的路径</returns>
        public static string UploadFile(string url, string filePath)
        {
            try
            {
                using (var client = GetClient())
                {
                    var responseData = client.UploadFile(url, filePath); //得到返回字符流

                    if (string.IsNullOrWhiteSpace(_sessionHeader))
                    {
                        _sessionHeader = client.ResponseHeaders["Set-Cookie"];//保存session
                    }
                    return Encoding.UTF8.GetString(responseData); //解码
                }
            }
            catch (WebException ex)
            {
                throw new Exception("无法连接服务器");
            }
        }

        private static WebClient GetClient()
        {
            return new WebClient
            {
                //webClient.Headers.Add("Cookie",header);//在给服务器发送消息时加上这个Session值
                Headers =
                {
                    [HttpRequestHeader.UserAgent] = "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; Trident/6.0)",
                    ["DNT"] = "1",
                    //["Content-Type"]="application/x-www-form-urlencoded",
                    ["Content-Type"]="application/json",
                    ["Cookie"]=_sessionHeader,
                    ["x-requested-with"]="XMLHttpRequest",
                },
                Encoding = Encoding.UTF8,
                BaseAddress = BaseUrl
            };
        }
    }