C#中POST数据和接收的几种方式（抛砖引玉）

POST方式提交数据，一种众所周知的方式：

html页面中使用form表单提交，接收方式，使用Request.Form[""]或Request.QueryString[""]来获取。

这里介绍另外一种POST方式和接收方式，就是将整个数据作为加入到数据流中提交和接收

接收方式:

Stream s = System.Web.HttpContext.Current.Request.InputStream;
byte[] b = new byte[s.Length];
s.Read(b, 0, (int)s.Length);
return Encoding.UTF8.GetString(b);

只需要从input Stream中读取byte数据，然后转为string，再解析即可。如果要回复响应消息只需要用：Response.Write()  输出即可（和普通的页面输出一样）。

主动POST发送方式：

            HttpWebRequest webrequest = (HttpWebRequest)HttpWebRequest.Create(url);
            webrequest.Method = "post";

            byte[] postdatabyte = Encoding.UTF8.GetBytes(postData);
            webrequest.ContentLength = postdatabyte.Length;
            Stream stream;
            stream = webrequest.GetRequestStream();
            stream.Write(postdatabyte, 0, postdatabyte.Length);
            stream.Close();

            using (var httpWebResponse = webrequest.GetResponse())
            using (StreamReader responseStream = new StreamReader(httpWebResponse.GetResponseStream()))
            {

                String ret = responseStream.ReadToEnd();

                T result = XmlDeserialize<T>(ret);

                return result;
            }

使用HttpClient对象发送

 public static  string   PostXmlResponse(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;
        }
         

从代码中可以看出仅仅是将字符串转为byte[] 类型，并加入到请求流中，进行请求即可达到POST效果，该种POST方式与上边所提到的接收方式相互配合使用。

下面一种方式是以键值对的方式主动POST传输的。

　　　　 /// <summary>
        /// 发起httpPost 请求，可以上传文件
        /// </summary>
        /// <param name="url">请求的地址</param>
        /// <param name="files">文件</param>
        /// <param name="input">表单数据</param>
        /// <param name="endoding">编码</param>
        /// <returns></returns>
        public static string PostResponse(string url, UpLoadFile[] files, Dictionary<string, string> input, Encoding endoding)
        {

            string boundary = "----------------------------" + DateTime.Now.Ticks.ToString("x");
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.ContentType = "multipart/form-data; boundary=" + boundary;
            request.Method = "POST";
            request.KeepAlive = true;
            //request.Credentials = CredentialCache.DefaultCredentials;
            request.Expect = "";

            MemoryStream stream = new MemoryStream();

            byte[] line = Encoding.ASCII.GetBytes("--" + boundary + "\r\n");
            byte[] enterER = Encoding.ASCII.GetBytes("\r\n");
            ////提交文件
            if (files != null)
            {
                string fformat = "Content-Disposition:form-data; name=\"{0}\";filename=\"{1}\"\r\nContent-Type:{2}\r\n\r\n";
                foreach (UpLoadFile file in files)
                {

                    stream.Write(line, 0, line.Length);        //项目分隔符
                    string s = string.Format(fformat, file.Name, file.FileName, file.Content_Type);
                    byte[] data = Encoding.UTF8.GetBytes(s);
                    stream.Write(data, 0, data.Length);
                    stream.Write(file.Data, 0, file.Data.Length);
                    stream.Write(enterER, 0, enterER.Length);  //添加\r\n
                }
            }

            //提交文本字段
            if (input != null)
            {
                string format = "--" + boundary + "\r\nContent-Disposition:form-data;name=\"{0}\"\r\n\r\n{1}\r\n";    //自带项目分隔符
                foreach (string key in input.Keys)
                {
                    string s = string.Format(format, key, input[key]);
                    byte[] data = Encoding.UTF8.GetBytes(s);
                    stream.Write(data, 0, data.Length);
                }

            }

            byte[] foot_data = Encoding.UTF8.GetBytes("--" + boundary + "--\r\n");      //项目最后的分隔符字符串需要带上--
            stream.Write(foot_data, 0, foot_data.Length);

            request.ContentLength = stream.Length;
            Stream requestStream = request.GetRequestStream(); //写入请求数据
            stream.Position = 0L;
            stream.CopyTo(requestStream); //
            stream.Close();

            requestStream.Close();

            try
            {

                HttpWebResponse response;
                try
                {
                    response = (HttpWebResponse)request.GetResponse();

                    try
                    {
                        using (var responseStream = response.GetResponseStream())
                        using (var mstream = new MemoryStream())
                        {
                            responseStream.CopyTo(mstream);
                            string message = endoding.GetString(mstream.ToArray());
                            return message;
                        }
                    }
                    catch (Exception ex)
                    {
                        throw ex;
                    }
                }
                catch (WebException ex)
                {
                    //response = (HttpWebResponse)ex.Response;

                    //if (response.StatusCode == HttpStatusCode.BadRequest)
                    //{
                    //    using (Stream data = response.GetResponseStream())
                    //    {
                    //        using (StreamReader reader = new StreamReader(data))
                    //        {
                    //            string text = reader.ReadToEnd();
                    //            Console.WriteLine(text);
                    //        }
                    //    }
                    //}

                    throw ex;
                }

            }
            catch (Exception ex)
            {
                throw ex;
            }
        }

通过两种主动POST提交 的代码可以看出，其主要区别在于发送前的数据格式 ContentType 的值。

下面列举几种常用的ContentType 值，并简述他们的区别

Content-Type 被指定为 application/x-www-form-urlencoded 时候，传输的数据格式需要如  title=test&sub%5B%5D=1&sub%5B%5D=2&sub%5B%5D=3 所示格式，才能正确解析

Content-Type 被指定为 multipart/form-data 时候，所需格式如下面代码块中所示

Content-Type:multipart/form-data; boundary=----WebKitFormBoundaryrGKCBY7qhFd3TrwA

------WebKitFormBoundaryrGKCBY7qhFd3TrwA

Content-Disposition: form-data; name="text"

title

------WebKitFormBoundaryrGKCBY7qhFd3TrwA

Content-Disposition: form-data; name="file"; filename="chrome.png"

Content-Type: image/png

PNG ... content of chrome.png ...

------WebKitFormBoundaryrGKCBY7qhFd3TrwA--

Content-Type 也可以被指定为 application/json ，最终传输格式为 {"title":"test","sub":[1,2,3]}  至于如何接收本人未经尝试，但是可以肯定的讲使用文章开头所说的接收方式接收后转为string类型再

发序列化是可行的。

Content-Type指定为 text/xml  ，传输的数据格式为

<?xml version="1.0"?>
<methodCall>
    <methodName>examples.getStateName</methodName>
    <params>
        <param>
            <value><i4>41</i4></value>
        </param>
    </params>
</methodCall>

此种方式，本人亦未经尝试，接受方式可以参考上文中 application/json 的接收方式。

由于xml的格式传输数据，使用相对较少，相信很多同学亦不知道如何将字符串解析为对象，下文将提供一种转换方式，供参考

            XmlDocument doc = new XmlDocument();
            doc.LoadXml(weixin);//读取xml字符串
            XmlElement root = doc.DocumentElement;

            ExmlMsg xmlMsg = new ExmlMsg()
            {
                FromUserName = root.SelectSingleNode("FromUserName").InnerText,
                ToUserName = root.SelectSingleNode("ToUserName").InnerText,
                CreateTime = root.SelectSingleNode("CreateTime").InnerText,
                MsgType = root.SelectSingleNode("MsgType").InnerText,
            };
            if (xmlMsg.MsgType.Trim().ToLower() == "text")
            {
                xmlMsg.Content = root.SelectSingleNode("Content").InnerText;
            }
            else if (xmlMsg.MsgType.Trim().ToLower() == "event")
            {
                xmlMsg.EventName = root.SelectSingleNode("Event").InnerText;
            }
            return xmlMsg;

        private class ExmlMsg
        {
            /// <summary>
            /// 本公众账号
            /// </summary>
            public string ToUserName { get; set; }
            /// <summary>
            /// 用户账号
            /// </summary>
            public string FromUserName { get; set; }
            /// <summary>
            /// 发送时间戳
            /// </summary>
            public string CreateTime { get; set; }
            /// <summary>
            /// 发送的文本内容
            /// </summary>
            public string Content { get; set; }
            /// <summary>
            /// 消息的类型
            /// </summary>
            public string MsgType { get; set; }
            /// <summary>
            /// 事件名称
            /// </summary>
            public string EventName { get; set; }

        }

至此，相信一部分同学能有所得。由于本人水平一般，文中所述可能有纰漏之处，还请路过高手指出，同时也欢迎在评论区贴出更好的 发送和接受方式，供大家学习和交流。

本文有参考：https://imququ.com/post/four-ways-to-post-data-in-http.html  ，向原文作者致谢。