Example of using C# to obtain the HTML source code of a web page-C#.Net Tutorial-php.cn

Example of using C# to obtain the HTML source code of a web page

高洛峰

Release： 2017-01-14 13:29:51

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I'm working on a project recently, and one of the functions is to get the source code of a web page based on a URL address. In ASP.NET (C#), there seem to be many ways to obtain the source code of a web page. I just made a simple WebClient, which is very simple and easy. But a very annoying problem came out later, and that was the garbled Chinese characters.

After careful study, Chinese web pages are nothing more than GB2312 and UTF-8. So we have the following code:

       /// <summary>
       /// 根据网址的URL，获取源代码HTML
       /// </summary>
       /// <param name="url"></param>
       /// <returns></returns>
       public static string GetHtmlByUrl(string url)
       {
           using (WebClient wc = new WebClient())
           {
               try
               {
                   wc.UseDefaultCredentials = true;
                   wc.Proxy = new WebProxy();
                   wc.Proxy.Credentials = CredentialCache.DefaultCredentials;
                   wc.Credentials = System.Net.CredentialCache.DefaultCredentials;
                   byte[] bt = wc.DownloadData(url);
                   string txt = System.Text.Encoding.GetEncoding("GB2312").GetString(bt);
                   switch (GetCharset(txt).ToUpper())
                   {
                       case "UTF-8":
                           txt = System.Text.Encoding.UTF8.GetString(bt);
                           break;
                       case "UNICODE":
                           txt = System.Text.Encoding.Unicode.GetString(bt);
                           break;
                       default:
                           break;
                   }
                   return txt;
               }
               catch (Exception ex)
               {
                   return null;
               }
           }
       }

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To explain a little bit, WebClient is used here to create a wc object (the naming is a bit awkward). Then call the DownloadData method of the wc object, pass in the URL value, and return a byte array. By default, GB2312 is used to read this byte array and convert it into a string. Find the characteristic characters of the encoding format of the web page from the string of the web page source code, such as finding information such as charset="utf-8", to determine the encoding format of the current web page.

The GetCharset function is used to obtain the encoding format of the current web page. The specific code is as follows:

      /// <summary>
       /// 从HTML中获取获取charset
       /// </summary>
       /// <param name="html"></param>
       /// <returns></returns>
       public static string GetCharset(string html)
       {
           string charset = "";
           Regex regCharset = new Regex(@"content=[""'].*\s*charset\b\s*=\s*""?(?<charset>[^""']*)", RegexOptions.IgnoreCase);
           if (regCharset.IsMatch(html))
           {
               charset = regCharset.Match(html).Groups["charset"].Value;
           }
           if (charset.Equals(""))
           {
               regCharset = new Regex(@"<\s*meta\s*charset\s*=\s*[""']?(?<charset>[^""']*)", RegexOptions.IgnoreCase);
               if (regCharset.IsMatch(html))
               {
                   charset = regCharset.Match(html).Groups["charset"].Value;
               }
           }
           return charset;
       }

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