Question

I am developing an application using twitter api and that involves writing a method to check if a user exists. Here is my code:

  public static bool checkUserExists(string user)
    {
        //string URL = "https://twitter.com/" + user.Trim();
        //string URL = "http://api.twitter.com/1/users/show.xml?screen_name=" + user.Trim();
        //string URL = "http://google.com/#hl=en&sclient=psy-ab&q=" + user.Trim();
        string URL = "http://api.twitter.com/1/users/show.json?screen_name=" + user.Trim();
        HttpWebRequest webRequest = (HttpWebRequest)WebRequest.Create(URL);
        try
        {
            var webResponse = (HttpWebResponse)webRequest.GetResponse();
            return true;
        }
        //this part onwards does not matter
        catch (WebException ex)
        {
            if (ex.Status == WebExceptionStatus.ProtocolError && ex.Response != null)
            {
                var resp = (HttpWebResponse)ex.Response;
                if (resp.StatusCode == HttpStatusCode.NotFound)
                {
                    return false;
                }
                else
                {
                    throw new Exception("Unknown level 1 Exception", ex);
                }
            }
            else
            {
                throw new Exception("Unknown level 2 Exception", ex);
            }
        }
    }

The problem is, calling the method does not work(it doesn’t get a response) more than 2 or 3 times, using any of the urls that have been commented, including the google search query(I thought it might be due to twitter API limit). On debug, it shows that it’s stuck at:

var webResponse = (HttpWebResponse)webRequest.GetResponse();

Here’s how I am calling it:

Console.WriteLine(TwitterFollowers.checkUserExists("handle1"));
Console.WriteLine(TwitterFollowers.checkUserExists("handle2"));
Console.WriteLine(TwitterFollowers.checkUserExists("handle3"));
Console.WriteLine(TwitterFollowers.checkUserExists("handle4"));
Console.WriteLine(TwitterFollowers.checkUserExists("handle5"));
Console.WriteLine(TwitterFollowers.checkUserExists("handle6"));

At most I get 2-3 lines of output. Could someone please point out what’s wrong?

Update 1:
I sent 1 request every 15 seconds (well within limit) and it still causes an error. on the other hand, sending a request, closing the app and running it again works very well (on average accounts to 1 request every 5 seconds). The rate limit is 150 calls per hour Twitter FAQ.

Also, I did wait for a while, and got this exception at level 2:
http://pastie.org/3897499

Update 2:
Might sound surprising but if I run fiddler, it works perfectly. Regardless of whether I target this process or not!

Answer 1

1. Note that you’re dealing with unmanaged resources underneath your HttpWebResponse. So calling Dispose() in a timely fashion or
   wrapping the object in a using statement is not only wise, but important to avoid blocking.
2. Also, var is great for dealing with anonymous types, Linq query
   results, and such but it should not become a crutch. Why use var
   when you’re well aware of the type? (i.e. you’re already performing
   a cast to HttpWebResponse.)
3. Finally, services like this often limit the rate of connections per second and/or the number of simultaneous connections allowed to prevent abuse. By not disposing of your HttpWebResponse objects, you may be violating the permitted number of simultaneous connections. By querying too often you’d break the rate limit.