Question

So I have a async Web Request method with a callback:

private void DoWebRequest(string url, string titleToCheckFor, 
                          Action<MyRequestState> callback)
{
  MyRequestState result = new MyRequestState();
  // ...
  // a lot of logic and stuff, and eventually return either:
  result.DoRedirect = false;
  // or:
  result.DoRedirect = true;
  callback(result);
}

(Just to point it out up front, my WebRequest.AllowAutoRedirect is set to false for a number of reasons)

I don’t know before hand how many redirects I can expect, so I started:

private void MyWrapperCall(string url, string expectedTitle, 
                          Action<MyRequestState> callback)
{
    DoWebRequest(url, expectedTitle, new Action<MyRequestState>((a) =>
    {
      if (a.DoRedirect)
      {
        DoWebRequest(a.Redirect, expectedTitle, new Action<MyRequestState>((b) =>
        {
          if (b.DoRedirect)
          {
            DoWebRequest(b.Redirect, expectedTitle, callback);
          }
        }));
      }
    }));
}

And now I got a brain meltdown, how could I put this is in an iterative loop so it does the last callback back to the original caller if no ReDirects are needed anymore?

Answer 1

Store a reference to the recursing method, so it can call itself:

private void MyWrapperCall(string url, string expectedTitle, Action<MyRequestState> callback)
{
    Action<MyRequestState> redirectCallback = null;
    redirectCallback = new Action<MyRequestState>((state) =>
    {
        if(state.DoRedirect)
        {
            DoWebRequest(state.Redirect, expectedTitle, redirectCallback);
        }
        else
        {
            callback(state);
        }
    });

    DoWebRequest(url, expectedTitle, redirectCallback);
}