第三节：总结.Net下后端的几种请求方式(WebClient、WebRequest、HttpClient)

一. 前言

　　前端调用有Form表单提交，ajax提交，ajax一般是用Jquery的简化写法，在这里不再过多介绍； 后端调用大约有这些：WebCient、WebRequest、Httpclient、WebapiClient，重点探讨Get和Post请求，Put和Delete请求用较少。

下面排着介绍Get和Post的基本写法，最后再封装一下，便于调用。

PS：其中Post请求有两种，分别是： "application/x-www-form-urlencoded"表单提交的方式 和 "application/json" Json格式提交的方式。

(1). Post的表单提交的格式为："userName=admin&pwd=123456"。

(2). Post的Json的提交格式为：将实体(类)转换成json字符串。

下面先编写几个服务器端的接口方法，便于调用。

        //Get http://localhost:2131/api/Forth/CheckLogin?userName=admin&pwd=123456
        [HttpGet]
        public string CheckLogin(string userName, string pwd)
        {
            if (userName == "admin" && pwd == "123456")
            {
                return "ok";
            }
            else
            {
                return "error";
            }
        }


        //Post http://localhost:2131/api/Forth/Register 
        [HttpPost]
        public string Register([FromBody]LoginModel model)
        {
            if (model.userName == "admin" && model.pwd == "123456")
            {
                return "ok";
            }
            else
            {
                return "error";
            }
        }

        //Post http://localhost:2131/api/Forth/Register2 
        [HttpPost]
        public string Register2([FromBody]dynamic model)
        {
            if (model.userName == "admin" && model.pwd == "123456")
            {
                return "ok";
            }
            else
            {
                return "error";
            }
        }

为了方便下面的测试，给上述三个地址进行命名描述和序列化方法的初始化

二. WebClient

 1. Get请求

WebClient wc = new WebClient();
string url = url1;
wc.Encoding = Encoding.UTF8;
string result = wc.DownloadString(url);
Console.WriteLine(result);
Console.ReadKey();

2. Post的表单提交方式（url2能访问，url3报500错误）

  WebClient wc = new WebClient();
  string url = url3;
  wc.Encoding = Encoding.UTF8;
  //也可以向表头中添加一些其他东西
  wc.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
  string result = wc.UploadString(url, "userName=admin&pwd=123456");
  Console.WriteLine(result);
  Console.ReadKey();

3. Post的JSON提交格式(url2和url3都能正常访问)

 var user = new
            {
               userName = "admin",
               pwd = "123456"
            };
 WebClient wc = new WebClient();
 string url = url3;
 wc.Encoding = Encoding.UTF8;
 wc.Headers.Add("Content-Type", "application/json");
10  string result = wc.UploadString(url, jss.Serialize(user));
 Console.WriteLine(result);
 Console.ReadKey();

三. WebRequest

1. Get请求

 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url1);
 request.Timeout = 30 * 1000;
 request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
 request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";
 string result = "";
 using (var res = request.GetResponse() as HttpWebResponse)
 {
    if (res.StatusCode == HttpStatusCode.OK)
    {
       StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
       result = reader.ReadToEnd();
    }
 }
 Console.WriteLine(result);
 Console.ReadKey();

2. Post的表单提交方式（url2能访问，url3报500错误）

                var postData = "userName=admin&pwd=123456";
                var request = HttpWebRequest.Create(url2) as HttpWebRequest;
                request.Timeout = 30 * 1000;//设置30s的超时
                request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
                request.ContentType = "application/x-www-form-urlencoded";
                request.Method = "POST";
                byte[] data = Encoding.UTF8.GetBytes(postData);
                request.ContentLength = data.Length;
                Stream postStream = request.GetRequestStream();
                postStream.Write(data, 0, data.Length);
                postStream.Close();
                string result = "";
                using (var res = request.GetResponse() as HttpWebResponse)
                {
                    if (res.StatusCode == HttpStatusCode.OK)
                    {
                        StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
                        result = reader.ReadToEnd();
                    }
                }
                Console.WriteLine(result);
                Console.ReadKey();

3. Post的JSON提交格式(url2和url3都能正常访问)

                var user = new
                {
                    userName = "admin",
                    pwd = "123456"
                };
                var postData = jss.Serialize(user);
                var request = HttpWebRequest.Create(url2) as HttpWebRequest;
                request.Timeout = 30 * 1000; //设置30s的超时
                request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
                request.ContentType = "application/json";
                request.Method = "POST";
                byte[] data = Encoding.UTF8.GetBytes(postData);
                request.ContentLength = data.Length;
                Stream postStream = request.GetRequestStream();
                postStream.Write(data, 0, data.Length);
                postStream.Close();
                string result = "";
                using (var res = request.GetResponse() as HttpWebResponse)
                {
                    if (res.StatusCode == HttpStatusCode.OK)
                    {
                        StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
                        result = reader.ReadToEnd();
                    }
                }
                Console.WriteLine(result);
                Console.ReadKey();

四. HttpClient

1. Get请求

 　　　　　　　　var handler = new HttpClientHandler();
                using (var http = new HttpClient(handler))
                {
                    var response = http.GetAsync(url1).Result;
                    //获取Http的状态值
                    //Console.WriteLine(response.StatusCode);
                    string result = response.Content.ReadAsStringAsync().Result;
                    Console.WriteLine(result);
                    Console.ReadKey();
                }

2. Post的表单提交方式（url2能访问，url3报500错误）

                var handler = new HttpClientHandler();
                using (var http = new HttpClient(handler))
                {
                    var content = new StringContent("userName=admin&pwd=123456", Encoding.UTF8, "application/x-www-form-urlencoded");
                    var response = http.PostAsync(url2, content).Result;
                    //获取Http的状态值
                    //Console.WriteLine(response.StatusCode);
                    string result = response.Content.ReadAsStringAsync().Result;
                    Console.WriteLine(result);
                    Console.ReadKey();
                }    

3. Post的JSON提交格式(url2和url3都能正常访问)

 　　　　　　　　var user = new
                {
                    userName = "admin",
                    pwd = "123456"
                };
                var handler = new HttpClientHandler();
                using (var http = new HttpClient(handler))
                {
                    var content = new StringContent(jss.Serialize(user), Encoding.UTF8, "application/json");
                    var response = http.PostAsync(url3, content).Result;
                    //获取Http的状态值
                    //Console.WriteLine(response.StatusCode);
                    string result = response.Content.ReadAsStringAsync().Result;
                    Console.WriteLine(result);
                    Console.ReadKey();
                }

注：以上代码均是官方的给出的标准写法，但存在很严重的问题，当请求量大的时候，会存在不能释放的问题，解决方案见下面。

解决方案：

　　将HttpClient做成单例的，不用Using，全局只有一个，来解决tcp连接不能释放的问题。

    /// <summary>
    /// 将HttpClient做成单例的，不用Using，全局只有一个
    /// 来解决tcp连接不能释放的问题
    /// </summary>
    public class HttpClientFactory
    {
        private static HttpClient _httpClient = null;

        /// <summary>
        /// 静态的构造函数：只能有一个，且是无参数的
        /// 由CLR保证，只有在程序第一次使用该类之前被调用，而且只能调用一次
        /// 说明： keep-alive关键字可以理解为一个长链接，超时时间也可以在上面进行设置，例如10秒的超时时间，当然并发量太大，这个10秒应该会抛弃很多请求
        /// 发送请求的代码没有了using，即这个httpclient不会被手动dispose，而是由系统控制它，当然你的程序重启时，这也就被回收了。
        /// </summary>
        static HttpClientFactory()
        {
            _httpClient = new HttpClient(new HttpClientHandler());
            _httpClient.Timeout = new TimeSpan(0, 0, 10);
            _httpClient.DefaultRequestHeaders.Connection.Add("keep-alive");
        }

        /// <summary>
        /// 对外开放接口
        /// </summary>
        /// <returns></returns>
        public static HttpClient GetHttpClient()
        {
            return _httpClient;
        }
    }

优化后调用进行Get和Post请求，代码如下

  　　　　　　　　var http = HttpClientFactory.GetHttpClient();
                //1.Get请求
                var response1 = http.GetAsync(url1).Result;
                var result1 = response1.Content.ReadAsStringAsync().Result;
                Console.WriteLine($"Get请求的返回值为：{result1}");
                //2. Post请求【application/x-www-form-urlencoded】
                var content2 = new StringContent("userName=admin&pwd=123456", Encoding.UTF8, "application/x-www-form-urlencoded");
                var response2 = http.PostAsync(url2, content2).Result;
                string result2 = response2.Content.ReadAsStringAsync().Result;
                Console.WriteLine($"Post请求【application/x-www-form-urlencoded】的返回值为：{result2}");
                //3. Post请求 【application/json】
                var user = new
                {
                    userName = "admin",
                    pwd = "123456"
                };
                var content3 = new StringContent(jss.Serialize(user), Encoding.UTF8, "application/json");
                var response3 = http.PostAsync(url3, content3).Result;
                string result3 = response3.Content.ReadAsStringAsync().Result;
                Console.WriteLine($"Post请求【application/json】的返回值为：{result3}");
                Console.ReadKey();

五. 扩展

 　　将WebClient、WebRequest、HttpClient三个类进行封装，其中HttpClient做成单例的，便于我们调用。

/// <summary>
    /// 总结各种请求方式
    /// </summary>
    public static class RequestWaysHelp
    {
        #region 01-WebClient的Get请求
        /// <summary>
        /// WebClient的Get请求
        /// </summary>
        /// <param name="url">请求地址,含拼接数据，请求格式为："http://XXXX?userName=admin&pwd=123456";</param>
        /// <returns></returns>
        public static string WcGet(string url)
        {
            WebClient wc = new WebClient();
            wc.Encoding = Encoding.UTF8;
            return wc.DownloadString(url);
        }
        #endregion

        #region 02-WebClient的Post请求
        /// <summary>
        /// WebClient的Post请求
        /// 表单提交模式[application/x-www-form-urlencoded]
        /// </summary>
        /// <param name="url">请求地址,单纯的地址,没有数据拼接</param>
        /// <param name="data">请求数据,格式为:"userName=admin&pwd=123456"</param>
        /// <returns></returns>
        public static string WcPost1(string url, string data)
        {
            WebClient wc = new WebClient();
            wc.Encoding = Encoding.UTF8;
            //也可以向表头中添加一些其他东西
            wc.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
            return wc.UploadString(url, data);
        }
        #endregion

        #region 03-WebClient的Post请求
        /// <summary>
        /// WebClient的Post请求
        /// Json提交模式[application/json]
        /// </summary>
        /// <param name="url">请求地址,单纯的地址,没有数据拼接</param>
        /// <param name="data">请求数据,格式为(Json)对象、或者类对象 eg： new {id="1"}</param>
        /// <returns></returns>
        public static string WcPost2(string url, object data)
        {
            JavaScriptSerializer jss = new JavaScriptSerializer();

            WebClient wc = new WebClient();
            wc.Encoding = Encoding.UTF8;
            //也可以向表头中添加一些其他东西
            wc.Headers.Add("Content-Type", "application/json");
            return wc.UploadString(url, jss.Serialize(data));
        }
        #endregion

        #region 04-HttpWebRequest的Get请求
        /// <summary>
        /// HttpWebRequest的Get请求
        /// </summary>
        /// <param name="url">请求地址,含拼接数据，请求格式为："http://XXXX?userName=admin&pwd=123456";</param>
        /// <returns></returns>
        public static string HwGet(string url)
        {
            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
            request.Timeout = 30 * 1000;
            request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
            request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";
            string result = "";
            using (var res = request.GetResponse() as HttpWebResponse)
            {
                if (res.StatusCode == HttpStatusCode.OK)
                {
                    StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
                    result = reader.ReadToEnd();
                }
            }
            return result;
        }
        #endregion

        #region 05-HttpWebRequest的Post请求
        /// <summary>
        /// HttpWebRequest的Post请求
        /// 表单提交模式[application/x-www-form-urlencoded]
        /// </summary>
        /// <param name="url">请求地址,单纯的地址,没有数据拼接</param>
        /// <param name="data">请求数据,格式为:"userName=admin&pwd=123456"</param>
        /// <returns></returns>
        public static string HwPost1(string url, string data)
        {
            var request = HttpWebRequest.Create(url) as HttpWebRequest;
            request.Timeout = 30 * 1000;//设置30s的超时
            request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
            request.ContentType = "application/x-www-form-urlencoded";
            request.Method = "POST";
            byte[] data2 = Encoding.UTF8.GetBytes(data);
            request.ContentLength = data2.Length;
            Stream postStream = request.GetRequestStream();
            postStream.Write(data2, 0, data2.Length);
            postStream.Close();
            string result = "";
            using (var res = request.GetResponse() as HttpWebResponse)
            {
                if (res.StatusCode == HttpStatusCode.OK)
                {
                    StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
                    result = reader.ReadToEnd();
                }
            }
            return result;
        }
        #endregion

        #region 06-HttpWebRequest的Post请求
        /// <summary>
        /// HttpWebRequest的Post请求
        /// Json提交模式[application/json]
        /// </summary>
        /// <param name="url">请求地址,单纯的地址,没有数据拼接</param>
        /// <param name="data">请求数据,格式为(Json)对象、或者类对象 eg： new {id="1"}</param>
        /// <returns></returns>
        public static string HwPost2(string url, object data)
        {
            JavaScriptSerializer jss = new JavaScriptSerializer();
            var postData = jss.Serialize(data);
            var request = HttpWebRequest.Create(url) as HttpWebRequest;
            request.Timeout = 30 * 1000; //设置30s的超时
            request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
            request.ContentType = "application/json";
            request.Method = "POST";
            byte[] data2 = Encoding.UTF8.GetBytes(postData);
            request.ContentLength = data2.Length;
            Stream postStream = request.GetRequestStream();
            postStream.Write(data2, 0, data2.Length);
            postStream.Close();
            string result = "";
            using (var res = request.GetResponse() as HttpWebResponse)
            {
                if (res.StatusCode == HttpStatusCode.OK)
                {
                    StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
                    result = reader.ReadToEnd();
                }
            }
            return result;
        }
        #endregion

        #region 07-HttpClient的Get请求
        /// <summary>
        /// HttpClient的Get请求
        /// </summary>
        ///<param name="url">请求地址,含拼接数据，请求格式为："http://XXXX?userName=admin&pwd=123456";</param>
        /// <returns></returns>
        public static string HcGet(string url)
        {
            var http = HttpClientFactory2.GetHttpClient();
            var response1 = http.GetAsync(url).Result;
            return  response1.Content.ReadAsStringAsync().Result;
        }
        #endregion

        #region 08-HttpClient的Post请求
        /// <summary>
        /// HttpClient的Post请求
        /// 表单提交模式[application/x-www-form-urlencoded]
        /// </summary>
        /// <param name="url">请求地址,单纯的地址,没有数据拼接</param>
        /// <param name="data">请求数据,格式为:"userName=admin&pwd=123456"</param>
        /// <returns></returns>
        public static string HcPost1(string url, string data)
        {
            var http = HttpClientFactory2.GetHttpClient();
            var content = new StringContent(data, Encoding.UTF8, "application/x-www-form-urlencoded");
            var response = http.PostAsync(url, content).Result;
            return response.Content.ReadAsStringAsync().Result;
        }
        #endregion

        #region 09-HttpClient的Post请求
        /// <summary>
        /// HttpClient的Post请求
        /// Json提交模式[application/json]
        /// </summary>
        /// <param name="url">请求地址,单纯的地址,没有数据拼接</param>
        /// <param name="data">请求数据,格式为(Json)对象、或者类对象 eg： new {id="1"}</param>
        /// <returns></returns>
        public static string HcPost2(string url, object data)
        {
            JavaScriptSerializer jss = new JavaScriptSerializer();
            var http = HttpClientFactory2.GetHttpClient();
            var content = new StringContent(jss.Serialize(data), Encoding.UTF8, "application/json");
            var response = http.PostAsync(url, content).Result;
            return response.Content.ReadAsStringAsync().Result;
        }
        #endregion


    }

    /// <summary>
    /// 将HttpClient做成单例的，不用Using，全局只有一个
    /// 来解决tcp连接不能释放的问题
    /// </summary>
    public class HttpClientFactory2
    {
        private static HttpClient _httpClient = null;

        /// <summary>
        /// 静态的构造函数：只能有一个，且是无参数的
        /// 由CLR保证，只有在程序第一次使用该类之前被调用，而且只能调用一次
        /// 说明： keep-alive关键字可以理解为一个长链接，超时时间也可以在上面进行设置，例如10秒的超时时间，当然并发量太大，这个10秒应该会抛弃很多请求
        /// 发送请求的代码没有了using，即这个httpclient不会被手动dispose，而是由系统控制它，当然你的程序重启时，这也就被回收了。
        /// </summary>
        static HttpClientFactory2()
        {
            _httpClient = new HttpClient(new HttpClientHandler());
            _httpClient.Timeout = new TimeSpan(0, 0, 10);
            _httpClient.DefaultRequestHeaders.Connection.Add("keep-alive");
        }

        /// <summary>
        /// 对外开放接口
        /// </summary>
        /// <returns></returns>
        public static HttpClient GetHttpClient()
        {
            return _httpClient;
        }
    }

封装后的调用：

　　　　　　　　  var user = new
                {
                    userName = "admin",
                    pwd = "123456"
                };
                // WebClient的相关测试
                {
                    Console.WriteLine("1.WebClient的相关测试");
                    var result1 = RequestWaysHelp.WcGet(url1);
                    Console.WriteLine(result1);
                    var result2 = RequestWaysHelp.WcPost1(url2, "userName=admin&pwd=123456");
                    Console.WriteLine(result2);
                    var result3 = RequestWaysHelp.WcPost2(url3, user);
                    Console.WriteLine(result3);
                }
                // HttpWebRequest的相关测试
                {
                    Console.WriteLine("2.HttpWebRequest的相关测试");
                    var result1 = RequestWaysHelp.HwGet(url1);
                    Console.WriteLine(result1);
                    var result2 = RequestWaysHelp.HwPost1(url2, "userName=admin&pwd=123456");
                    Console.WriteLine(result2);
                    var result3 = RequestWaysHelp.HwPost2(url3, user);
                    Console.WriteLine(result3);
                }
                // HttpClient的相关测试
                {
                    Console.WriteLine("3.HttpClient的相关测试");
                    var result1 = RequestWaysHelp.HcGet(url1);
                    Console.WriteLine(result1);
                    var result2 = RequestWaysHelp.HcPost1(url2, "userName=admin&pwd=123456");
                    Console.WriteLine(result2);
                    var result3 = RequestWaysHelp.HcPost2(url3, user);
                    Console.WriteLine(result3);
                }

!

• 作       者 : Yaopengfei(姚鹏飞)
• 博客地址 : http://www.cnblogs.com/yaopengfei/
• 声     明1 : 本人才疏学浅，用郭德纲的话说“我是一个小学生”，如有错误，欢迎讨论，请勿谩骂^_^。
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