HttpClient后台post 请求webapi

1.请求方法
       /// <summary>
        ///  httpClient 请求接口
        /// </summary>
        /// <param name="url">地址</param>
        /// <param name="xmlString">提交数据 json格式</param>
        /// <returns></returns>
        private string PostResponse(string url, string xmlString)
        {

            HttpContent httpContent = new StringContent(xmlString);
            httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
            HttpClient httpClient = new HttpClient();

            HttpResponseMessage response = httpClient.PostAsync(url, httpContent).Result;

            if (response.IsSuccessStatusCode)
            {
                Task<string> t = response.Content.ReadAsStringAsync();
                return t.Result;
            }
            return string.Empty;
        }

　　

 2.Api
      // POST api/values  
       public HttpResponseMessage Post([FromBody]string value)  
       {  
           return Request.CreateResponse(HttpStatusCode.OK, value);  
       }