一. 前言
前端調用有Form表單提交，ajax提交，ajax一般是用Jquery的簡化寫法，在這裏不再過多介紹； 後端調用大約有這些：WebCient、WebRequest、Httpclient、WebapiClient，重點探討Get和Post請求，Put和Delete請求用較少。
下面排着介紹Get和Post的基本寫法，最後再封裝一下，便於調用。
PS：其中Post請求有兩種，分別是： "application/x-www-form-urlencoded"表單提交的方式 和 "application/json" Json格式提交的方式。
(1). Post的表單提交的格式爲："userName=admin&pwd=123456"。
(2). Post的Json的提交格式爲：將實體(類)轉換成json字符串。
下面先編寫幾個服務器端的接口方法，便於調用。
1 //Get http://localhost:2131/api/Forth/CheckLogin?userName=admin&pwd=123456
2 [HttpGet]
3 public string CheckLogin(string userName, string pwd)
4 {
5 if (userName == "admin" && pwd == "123456")
6 {
7 return "ok";
8 }
9 else
10 {
11 return "error";
12 }
13 }
14
15
16 //Post http://localhost:2131/api/Forth/Register
17 [HttpPost]
18 public string Register([FromBody]LoginModel model)
19 {
20 if (model.userName == "admin" && model.pwd == "123456")
21 {
22 return "ok";
23 }
24 else
25 {
26 return "error";
27 }
28 }
29
30 //Post http://localhost:2131/api/Forth/Register2
31 [HttpPost]
32 public string Register2([FromBody]dynamic model)
33 {
34 if (model.userName == "admin" && model.pwd == "123456")
35 {
36 return "ok";
37 }
38 else
39 {
40 return "error";
41 }
42 }
爲了方便下面的測試，給上述三個地址進行命名描述和序列化方法的初始化
二. WebClient
1. Get請求
1 WebClient wc = new WebClient(); 2 string url = url1; 3 wc.Encoding = Encoding.UTF8; 4 string result = wc.DownloadString(url); 5 Console.WriteLine(result); 6 Console.ReadKey();
2. Post的表單提交方式（url2能訪問，url3報500錯誤）
1 WebClient wc = new WebClient();
2 string url = url3;
3 wc.Encoding = Encoding.UTF8;
4 //也可以向表頭中添加一些其他東西
5 wc.Headers.Add("Content-Type", "application/x-www-form-urlencoded");
6 string result = wc.UploadString(url, "userName=admin&pwd=123456");
7 Console.WriteLine(result);
8 Console.ReadKey();
3. Post的JSON提交格式(url2和url3都能正常訪問)
1 var user = new
2 {
3 userName = "admin",
4 pwd = "123456"
5 };
6 WebClient wc = new WebClient();
7 string url = url3;
8 wc.Encoding = Encoding.UTF8;
9 wc.Headers.Add("Content-Type", "application/json");
10 string result = wc.UploadString(url, jss.Serialize(user));
11 Console.WriteLine(result);
12 Console.ReadKey();
三. WebRequest
1. Get請求
1 HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url1);
2 request.Timeout = 30 * 1000;
3 request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
4 request.ContentType = "application/x-www-form-urlencoded; charset=UTF-8";
5 string result = "";
6 using (var res = request.GetResponse() as HttpWebResponse)
7 {
8 if (res.StatusCode == HttpStatusCode.OK)
9 {
10 StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
11 result = reader.ReadToEnd();
12 }
13 }
14 Console.WriteLine(result);
15 Console.ReadKey();
2. Post的表單提交方式（url2能訪問，url3報500錯誤）
1 var postData = "userName=admin&pwd=123456";
2 var request = HttpWebRequest.Create(url2) as HttpWebRequest;
3 request.Timeout = 30 * 1000;//設置30s的超時
4 request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
5 request.ContentType = "application/x-www-form-urlencoded";
6 request.Method = "POST";
7 byte[] data = Encoding.UTF8.GetBytes(postData);
8 request.ContentLength = data.Length;
9 Stream postStream = request.GetRequestStream();
10 postStream.Write(data, 0, data.Length);
11 postStream.Close();
12 string result = "";
13 using (var res = request.GetResponse() as HttpWebResponse)
14 {
15 if (res.StatusCode == HttpStatusCode.OK)
16 {
17 StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
18 result = reader.ReadToEnd();
19 }
20 }
21 Console.WriteLine(result);
22 Console.ReadKey();
3. Post的JSON提交格式(url2和url3都能正常訪問)
1 var user = new
2 {
3 userName = "admin",
4 pwd = "123456"
5 };
6 var postData = jss.Serialize(user);
7 var request = HttpWebRequest.Create(url2) as HttpWebRequest;
8 request.Timeout = 30 * 1000; //設置30s的超時
9 request.UserAgent = "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2272.118 Safari/537.36";
10 request.ContentType = "application/json";
11 request.Method = "POST";
12 byte[] data = Encoding.UTF8.GetBytes(postData);
13 request.ContentLength = data.Length;
14 Stream postStream = request.GetRequestStream();
15 postStream.Write(data, 0, data.Length);
16 postStream.Close();
17 string result = "";
18 using (var res = request.GetResponse() as HttpWebResponse)
19 {
20 if (res.StatusCode == HttpStatusCode.OK)
21 {
22 StreamReader reader = new StreamReader(res.GetResponseStream(), Encoding.UTF8);
23 result = reader.ReadToEnd();
24 }
25 }
26 Console.WriteLine(result);
27 Console.ReadKey();
四. HttpClient
1. Get請求
1 var handler = new HttpClientHandler();
2 using (var http = new HttpClient(handler))
3 {
4 var response = http.GetAsync(url1).Result;
5 //獲取Http的狀態值
6 //Console.WriteLine(response.StatusCode);
7 string result = response.Content.ReadAsStringAsync().Result;
8 Console.WriteLine(result);
9 Console.ReadKey();
10 }
2. Post的表單提交方式（url2能訪問，url3報500錯誤）
1 var handler = new HttpClientHandler();
2 using (var http = new HttpClient(handler))
3 {
4 var content = new StringContent("userName=admin&pwd=123456", Encoding.UTF8, "application/x-www-form-urlencoded");
5 var response = http.PostAsync(url2, content).Result;
6 //獲取Http的狀態值
7 //Console.WriteLine(response.StatusCode);
8 string result = response.Content.ReadAsStringAsync().Result;
9 Console.WriteLine(result);
10 Console.ReadKey();
11 }
3. Post的JSON提交格式(url2和url3都能正常訪問)
1 var user = new
2 {
3 userName = "admin",
4 pwd = "123456"
5 };
6 var handler = new HttpClientHandler();
7 using (var http = new HttpClient(handler))
8 {
9 var content = new StringContent(jss.Serialize(user), Encoding.UTF8, "application/json");
10 var response = http.PostAsync(url3, content).Result;
11 //獲取Http的狀態值
12 //Console.WriteLine(response.StatusCode);
13 string result = response.Content.ReadAsStringAsync().Result;
14 Console.WriteLine(result);
15 Console.ReadKey();
16 }
注：以上代碼均是官方的給出的標準寫法，但存在很嚴重的問題，當請求量大的時候，會存在不能釋放的問題，解決方案見下面。
解決方案：
將HttpClient做成單例的，不用Using，全局只有一個，來解決tcp連接不能釋放的問題。
1 /// <summary>
2 /// 將HttpClient做成單例的，不用Using，全局只有一個
3 /// 來解決tcp連接不能釋放的問題
4 /// </summary>
5 public class HttpClientFactory
6 {
7 private static HttpClient _httpClient = null;
8
9 /// <summary>
10 /// 靜態的構造函數：只能有一個，且是無參數的
11 /// 由CLR保證，只有在程序第一次使用該類之前被調用，而且只能調用一次
12 /// 說明： keep-alive關鍵字可以理解爲一個長鏈接，超時時間也可以在上面進行設置，例如10秒的超時時間，當然併發量太大，這個10秒應該會拋棄很多請求
13 /// 發送請求的代碼沒有了using，即這個httpclient不會被手動dispose，而是由系統控制它，當然你的程序重啓時，這也就被回收了。
14 /// </summary>
15 static HttpClientFactory()
16 {
17 _httpClient = new HttpClient(new HttpClientHandler());
18 _httpClient.Timeout = new TimeSpan(0, 0, 10);
19 _httpClient.DefaultRequestHeaders.Connection.Add("keep-alive");
20 }
21
22 /// <summary>
23 /// 對外開放接口
24 /// </summary>
25 /// <returns></returns>
26 public static HttpClient GetHttpClient()
27 {
28 return _httpClient;
29 }
30 }
優化後調用進行Get和Post請求，代碼如下
1 var http = HttpClientFactory.GetHttpClient();
2 //1.Get請求
3 var response1 = http.GetAsync(url1).Result;
4 var result1 = response1.Content.ReadAsStringAsync().Result;
5 Console.WriteLine($"Get請求的返回值爲：{result1}");
6 //2. Post請求【application/x-www-form-urlencoded】
7 var content2 = new StringContent("userName=admin&pwd=123456", Encoding.UTF8, "application/x-www-form-urlencoded");
8 var response2 = http.PostAsync(url2, content2).Result;
9 string result2 = response2.Content.ReadAsStringAsync().Result;
10 Console.WriteLine($"Post請求【application/x-www-form-urlencoded】的返回值爲：{result2}");
11 //3. Post請求 【application/json】
12 var user = new
13 {
14 userName = "admin",
15 pwd = "123456"
16 };
17 var content3 = new StringContent(jss.Serialize(user), Encoding.UTF8, "application/json");
18 var response3 = http.PostAsync(url3, content3).Result;
19 string result3 = response3.Content.ReadAsStringAsync().Result;
20 Console.WriteLine($"Post請求【application/json】的返回值爲：{result3}");
21 Console.ReadKey();
五. 擴展
將WebClient、WebRequest、HttpClient三個類進行封裝，其中HttpClient做成單例的，便於我們調用。
RequestWaysHelp封裝後的調用：
1 var user = new
2 {
3 userName = "admin",
4 pwd = "123456"
5 };
6 // WebClient的相關測試
7 {
8 Console.WriteLine("1.WebClient的相關測試");
9 var result1 = RequestWaysHelp.WcGet(url1);
10 Console.WriteLine(result1);
11 var result2 = RequestWaysHelp.WcPost1(url2, "userName=admin&pwd=123456");
12 Console.WriteLine(result2);
13 var result3 = RequestWaysHelp.WcPost2(url3, user);
14 Console.WriteLine(result3);
15 }
16 // HttpWebRequest的相關測試
17 {
18 Console.WriteLine("2.HttpWebRequest的相關測試");
19 var result1 = RequestWaysHelp.HwGet(url1);
20 Console.WriteLine(result1);
21 var result2 = RequestWaysHelp.HwPost1(url2, "userName=admin&pwd=123456");
22 Console.WriteLine(result2);
23 var result3 = RequestWaysHelp.HwPost2(url3, user);
24 Console.WriteLine(result3);
25 }
26 // HttpClient的相關測試
27 {
28 Console.WriteLine("3.HttpClient的相關測試");
29 var result1 = RequestWaysHelp.HcGet(url1);
30 Console.WriteLine(result1);
31 var result2 = RequestWaysHelp.HcPost1(url2, "userName=admin&pwd=123456");
32 Console.WriteLine(result2);
33 var result3 = RequestWaysHelp.HcPost2(url3, user);
34 Console.WriteLine(result3);
35 }