cs端调用webApi

public class Httphelper
    {
        public static string Post1(string url, string postString)
        {
            
            using (WebClient webClient = new WebClient())
            {
                byte[] postData = Encoding.UTF8.GetBytes(postString);//编码，
                webClient.Headers.Add("Content-Type", "application/json");//采取POST方式必须加的header，如果改为GET方式的话就去掉这句话即可  
                byte[] responseData = webClient.UploadData(url, "POST", postData);//得到返回字符流  
                string srcString = Encoding.UTF8.GetString(responseData);//解码  
                return srcString;
            }
        }

        public static string Post(string url, string postData)
        {
            string result = "";

            HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);

            req.Method = "POST";

           

            req.ContentType = "application/json";

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

            req.ContentLength = data.Length;
            //req.Timeout = 30000;
            using (Stream reqStream = req.GetRequestStream())
            {
                reqStream.Write(data, 0, data.Length);

                reqStream.Close();
            }

            HttpWebResponse resp = (HttpWebResponse)req.GetResponse();

            Stream stream = resp.GetResponseStream();

            //获取响应内容
            using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
            {
                result = reader.ReadToEnd();
            }
           
            return result;
        }
    }

 HttpClient 调用

 /// <summary>
        /// post 同步
        /// </summary>
        /// <param name="url"></param>
        /// <param name="postString"></param>
        /// <returns></returns>
        public static string Post(string url, string postData)
        {
            try
            {
                using (HttpClient _httpClient = new HttpClient())
                {
                    StringContent httpClient = new StringContent(postData, Encoding.UTF8, "application/json");
                    var response = _httpClient.PostAsync(url, httpClient).Result;
                    string jsonstr = response.Content.ReadAsStringAsync().Result;
                    return jsonstr;
                }
            }
            catch (Exception ex)
            {
                _logger.LogError(string.Format("Api调用异常--url【{0}】,参数【{1}】", url, postData), ex);
                return "";
            }
        }
        /// <summary>
        /// post 异步
        /// </summary>
        /// <param name="url"></param>
        /// <param name="postData"></param>
        /// <returns></returns>
        public static async void PostAsync(string url, string postData)
        {
            try
            {
                using (HttpClient _httpClient = new HttpClient())
                {
                    StringContent httpClient = new StringContent(postData, Encoding.UTF8, "application/json");
                    var response = await _httpClient.PostAsync(url, httpClient);
                    string jsonstr = await response.Content.ReadAsStringAsync();
                }
            }
            catch (Exception ex)
            {
                _logger.LogError(string.Format("Api调用异常--url【{0}】,参数【{1}】", url, postData), ex);
            }
        }