C#使用WebClient时，如果状态码不为200时，如何获取请求返回的内容

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一、事故现场

使用WebClient发送请求，如果返回的状态码不是2xx或3xx，那么默认情况下会抛出异常，
那如何才能获取到请求返回的内容呢？

二、解决方法

可以通过try catch获取到WebException类型的异常；

• api接口：

   [HttpGet("test")]
   public ActionResult test()
   {
       Response.StatusCode = 401;
       return Content("test");
   }

• 使用WebClient发送请求：
  方式一：直接捕获WebException 类型异常；

   public static string WebClientGetRequest(string url)
   {
       try
       {
           using (WebClient client = new WebClient())
           {
               //设置编码格式
               client.Encoding = System.Text.Encoding.UTF8;
               //获取数据
               var result = client.DownloadString(url);
               return result;
           }
       }
       catch (WebException ex)
       {
           using (HttpWebResponse hr = (HttpWebResponse)ex.Response)
           {
               int statusCode = (int)hr.StatusCode;
               StringBuilder sb = new StringBuilder();
               StreamReader sr = new StreamReader(hr.GetResponseStream(), Encoding.UTF8);
               sb.Append(sr.ReadToEnd());
               Console.WriteLine("StatusCode:{0},Content:{1}", statusCode, sb);// StatusCode:401,Content:test
           }
           return "";
       }
   }

方法二：捕获 Exception 异常，然后再判断异常类型；

   public static string WebClientGetRequest(string url)
   {
       try
       {
           using (WebClient client = new WebClient())
           {
               //设置编码格式
               client.Encoding = System.Text.Encoding.UTF8;
               //获取数据
               var result = client.DownloadString(url);
               return result;
           }
       }
       catch (WebException ex)
       {
           if (ex.GetType().Name == "WebException")
           {
               WebException we = (WebException)ex;
               using (HttpWebResponse hr = (HttpWebResponse)we.Response)
               {
                   int statusCode = (int)hr.StatusCode;
                   StringBuilder sb = new StringBuilder();
                   StreamReader sr = new StreamReader(hr.GetResponseStream(), Encoding.UTF8);
                   sb.Append(sr.ReadToEnd());
                   Console.WriteLine("StatusCode:{0},Content:{1}", statusCode, sb);// StatusCode:401,Content:test
               }
           }
           return "";
       }
   }

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