title: Understanding compiler-generated type in dotPeek decompiled code
body: <p>Hei. I was reading <code>Digi Traffic Accelerator</code>'s decompiled source (I think it is the best way to learn), until I got some non-understandable code! Please take a look:</p>
  
  <pre><code>  internal class ProxyFarm
    {
      private static Random rand = new Random();
      private static Regex UserPassAtHostPort = new Regex("\r\n                ^\r\n                (?&lt;user&gt;[^:]+?) : (?&lt;pass&gt;[^@]+?)\r\n                @\r\n                (?&lt;host&gt;[^:]+? (?: : \\d+)? )\r\n                $", RegexOptions.IgnorePatternWhitespace);
      private static Regex HostPortUserPass = new Regex("\r\n                ^\r\n                (?&lt;host&gt;[^:]+? : \\d+) : (?&lt;user&gt;[^:]+?) : (?&lt;pass&gt;.+?)\r\n                $", RegexOptions.IgnorePatternWhitespace);
      public const string NEW = "new";
      public const string ACTIVE = "active";
      public const string BLOCKED_BY_GOOGLE = "blocked by Google";
      public const string INACTIVE = "inactive";
      public const string CHECKING = "Checking...";
  
      static ProxyFarm()
      {
      }
  
      public static StorageDataSet.ProxiesRow GetRandomProxy(bool WillUseRecaptcha = true)
      {
        // some normal code
      }
  
      public static WebProxy MakeWebProxy(StorageDataSet.ProxiesRow row)
      {
        // some normal code
      }
  
      public static void CheckProxy(StorageDataSet.ProxiesRow proxy)
      {
        // ISSUE: object of a compiler-generated type is created
        // ISSUE: variable of a compiler-generated type
        ProxyFarm.\u003C\u003Ec__DisplayClass5 cDisplayClass5 = new ProxyFarm.\u003C\u003Ec__DisplayClass5();
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.proxy = proxy;
        // ISSUE: reference to a compiler-generated field
        if (cDisplayClass5.proxy == null)
          return;
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.logger = LogManager.GetLogger("Program");
        // ISSUE: reference to a compiler-generated field
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.state = new ProxyFarm.CallbackState()
        {
          Proxy = cDisplayClass5.proxy,
          Google = ProxyFarm.CheckStatus.NotChecked,
          Post = ProxyFarm.CheckStatus.NotChecked
        };
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.r = (HttpWebRequest) WebRequest.Create("http://www.digitrafficgenerator.com/post_test.php");
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.r.Method = "POST";
        try
        {
          // ISSUE: reference to a compiler-generated field
          // ISSUE: reference to a compiler-generated field
          cDisplayClass5.r.Proxy = (IWebProxy) ProxyFarm.MakeWebProxy(cDisplayClass5.proxy);
        }
        catch (Exception ex)
        {
          // ISSUE: reference to a compiler-generated field
          // ISSUE: reference to a compiler-generated field
          cDisplayClass5.logger.Warn((object) ("Invalid proxy entered: " + cDisplayClass5.proxy.Address), ex);
          // ISSUE: reference to a compiler-generated field
          ProxyFarm.ChangeStatus(cDisplayClass5.proxy, "inactive");
          return;
        }
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.r.ConnectionGroupName = Guid.NewGuid().ToString();
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.byteArray = Encoding.UTF8.GetBytes("q=test");
        // ISSUE: reference to a compiler-generated field
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.r.ContentLength = (long) cDisplayClass5.byteArray.Length;
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.r.ContentType = "application/x-www-form-urlencoded";
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.r.Referer = "http://www.digitrafficgenerator.com/post_test.php";
        // ISSUE: reference to a compiler-generated field
        cDisplayClass5.r.Timeout = 20000;
        // ISSUE: reference to a compiler-generated field
        // ISSUE: reference to a compiler-generated method
        IAsyncResult res = cDisplayClass5.r.BeginGetRequestStream(new AsyncCallback(cDisplayClass5.\u003CCheckProxy\u003Eb__1), (object) null);
        // ISSUE: reference to a compiler-generated field
        WebObject.AbortRequestAfterTimeout(res, cDisplayClass5.r);
        try
        {
          // ISSUE: reference to a compiler-generated field
          // ISSUE: reference to a compiler-generated method
          // ISSUE: reference to a compiler-generated field
          res = cDisplayClass5.r.BeginGetResponse(new AsyncCallback(cDisplayClass5.\u003CCheckProxy\u003Eb__2), (object) cDisplayClass5.r);
        }
        catch (Exception ex)
        {
          // ISSUE: reference to a compiler-generated field
          // ISSUE: reference to a compiler-generated field
          cDisplayClass5.logger.Info((object) ("Got an exception using " + cDisplayClass5.proxy.Address), ex);
        }
        // ISSUE: reference to a compiler-generated field
        WebObject.AbortRequestAfterTimeout(res, cDisplayClass5.r);
        HttpWebRequest request = (HttpWebRequest) WebRequest.Create("http://www.google.com/recaptcha/api/js/recaptcha.js");
        request.Method = "GET";
        // ISSUE: reference to a compiler-generated field
        request.Proxy = (IWebProxy) ProxyFarm.MakeWebProxy(cDisplayClass5.proxy);
        request.Timeout = 20000;
        request.ConnectionGroupName = Guid.NewGuid().ToString();
        // ISSUE: reference to a compiler-generated method
        WebObject.AbortRequestAfterTimeout(request.BeginGetResponse(new AsyncCallback(cDisplayClass5.\u003CCheckProxy\u003Eb__3), (object) request), request);
      }
  
      protected static void ProxyChecked(IAsyncResult result, HttpWebRequest req, ProxyFarm.CallbackState state)
      {
        ILog logger = LogManager.GetLogger("Program");
        ProxyFarm.CheckStatus checkStatus = ProxyFarm.CheckStatus.NotOk;
        try
        {
          HttpWebResponse httpWebResponse = (HttpWebResponse) req.EndGetResponse(result);
          if (req.RequestUri == httpWebResponse.ResponseUri)
          {
            if (httpWebResponse.StatusCode == HttpStatusCode.OK)
              checkStatus = ProxyFarm.CheckStatus.Ok;
          }
        }
        catch (Exception ex)
        {
        }
        lock (state)
        {
          if (req.RequestUri.Authority.Contains("google.com"))
            state.Google = checkStatus;
          else
            state.Post = checkStatus;
          if (state.Post == ProxyFarm.CheckStatus.NotOk)
          {
            ProxyFarm.ChangeStatus(state.Proxy, "inactive");
            logger.Info((object) ("Marking " + state.Proxy.Address + " as inactive as it cannot POST"));
          }
          else if (state.Google == ProxyFarm.CheckStatus.NotOk)
          {
            ProxyFarm.ChangeStatus(state.Proxy, "inactive");
            logger.Info((object) ("Marking " + state.Proxy.Address + " as inactive as it is blocked by google"));
          }
          else
          {
            if (state.Google != ProxyFarm.CheckStatus.Ok || state.Post != ProxyFarm.CheckStatus.Ok)
              return;
            ProxyFarm.ChangeStatus(state.Proxy, "active");
          }
        }
      }
  
      public static void ReportBrokenProxy(StorageDataSet.ProxiesRow proxy, bool recaptcha_fail = false)
      {
        // some normal code
      }
  
      private static void ChangeStatus(StorageDataSet.ProxiesRow Proxy, string status)
      {
        // some normal code
      }
  
      public enum CheckStatus
      {
        NotChecked,
        Ok,
        NotOk,
      }
  
      protected class CallbackState
      {
        public StorageDataSet.ProxiesRow Proxy { get; set; }
  
        public ProxyFarm.CheckStatus Post { get; set; }
  
        public ProxyFarm.CheckStatus Google { get; set; }
      }
    }
  </code></pre>
  
  <p>As you can see, it seems in <code>CheckProxy</code> method, the compiler generated a new type! Do you have any idea what is really happening in this method? How can I understand the code?</p>