先说一下问题，由于之前公共方法用的都不是异步方法，所以没办法将方法改为async方法
也就导致 postansy方法无法使用 因为一旦用了返回就变为Task<>

  List<RealtimeData> realtimeDatas = new List<RealtimeData>();
            string source = "";
            //先将两条数据更新到数据库中
            foreach (var item in server.Points)
            {
                source += "/" + item.Source + ",";
            }
            ///请求对方接口 
            var res = "";
            HttpClient _httpClient = new HttpClient();
            var postContent = new MultipartFormDataContent(); 
            var requestUri = server.HostName;


            var values = new[]
            {
                 new KeyValuePair<string, string>("id","1"), 
                 };

            foreach (var keyValuePair in values)
            {
                postContent.Add(new StringContent(keyValuePair.Value),
                    String.Format("\"{0}\"", keyValuePair.Key));
            }
          var response =   Getcon(requestUri, postContent); 
            //处理返回JSON数据
            var q = JsonConvert.DeserializeObject<List<XNYQM>>(response);
             

            }

注意 关键是Getcon方法如何返回不是Task格式

 public  static  string Getcon(string requestUri, MultipartFormDataContent postContent)
        { 
            HttpClient _httpClient = new HttpClient();
            var response = _httpClient.PostAsync(requestUri, postContent);
            
               response.Wait();
            var t2 = response.Result.Content.ReadAsByteArrayAsync();
            string str = System.Text.Encoding.UTF8.GetString(t2.Result);
            return str;
        } 

这里将接口返回的值进行byte转码就可以返回正常的string 然后在进行处理就可以了