最近写个项目，是提供接口的项目，项目使用java编写的，但是客户需要用C# 调用这套接口，一开始我没太关注，因为postman都正常调用，但是在写C# 调用Demo时出现问题了。

public static void Test()
        {
            string result = DoPost("http://ip:port/user/login", PreparationParameters());
        }

        private static Dictionary<string, object> PreparationParameters()
        {
            return new Dictionary<string, object>()
            {
                { "username","test"},
                { "secret", "test"}
            };
        }

        private static string DoPost(string url, object param)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.Accept = "*/*";
            request.ContentType = "application/json";
            //request.Timeout = Timeout.Infinite;
            request.Timeout = 80000;
            request.Method = "Post";
            request.Proxy = null;

            string json = JsonConvert.SerializeObject(param);
            byte[] data = Encoding.UTF8.GetBytes(json);
            request.ContentLength = data.Length;
            using(Stream stream = request.GetRequestStream())
            {
                stream.Write(data, 0, data.Length);
                stream.Flush();
            }

            using (StreamReader reader = new StreamReader(request.GetResponse().GetResponseStream()))
            {
                string result = reader.ReadToEnd();
                return result;
            }
        }

如上图显示，出现问题是我传递的参数总是为空，也就是我C# 传递的参数，java接收不到，一开始考虑的是不是ContentType的问题，换了别的还是参数传递不过去，没办法，我用java代码测试了一下

public static String Post(String URL, Map<String, Object> parameter){

        try{
            return HttpRequest.post(URL)
                    .form(parameter).timeout(20000).execute().body();
        }catch (Exception ex){
            return String.format("异常：{0}", ex.getMessage());
        }

    }

神奇的是java这样传递的话，接口能够正常接收到参数，并且正常调用.

public static void Test()
        {
            string result = DoPost("http://ip:port/user/login", PreparationParameters());
        }

        private static NameValueCollection PreparationParameters()
        {
            return new NameValueCollection
            {
                { "username", "test" },
                { "secret", "test" }
            };
        }

        private static string DoPost(string url, NameValueCollection param)
        {
            using (WebClient webClient = new WebClient())
            {
                try
                {
                    byte[] remoteInfo = webClient.UploadValues(url, "POST", param);
                    string result = Encoding.UTF8.GetString(remoteInfo);
                    return result;
                }
                catch (Exception ex)
                {
                    return ex.Message;
                }
            }

        }

最后代码改成这个样子，可以了，能够正常调用了，但是个中原委，还是不太清楚，这次记录一下，有机会再研究吧