How to programatically lengthen shortened urls

Question

I need to get the url of the final destination of a shortened url. At the moment I am doing the following which seems to work:

        var request = WebRequest.Create(shortenedUri);
        var response = request.GetResponse();
        return response.ResponseUri;

But can anyone suggest a better way?

Answer 1

You do need to make an HTTP request - but you don't need to follow the redirect, which WebRequest will do by default. Here's a short example of making just one request:

using System;
using System.Net;

class Test
{
    static void Main()
    {
        string url = "http://tinyurl.com/so-hints";
        Console.WriteLine(LengthenUrl(url));
    }

    static string LengthenUrl(string url)
    {
        var request = WebRequest.CreateHttp(url);
        request.AllowAutoRedirect = false;
        using (var response = request.GetResponse())
        {
            var status = ((HttpWebResponse) response).StatusCode;
            if (status == HttpStatusCode.Moved ||
                status == HttpStatusCode.MovedPermanently)
            {
                return response.Headers["Location"];
            }
            // TODO: Work out a better exception
            throw new Exception("No redirect required.");
        }
    }
}

Note that this means if the "lengthened" URL is itself a redirect, you won't get the "final" URI as you would in your original code. Likewise if the lengthened URL is invalid, you won't spot that - you'll just get the URL that you would have redirected to. Whether that's a good thing or not depends on your use case...