Getting the Redirected URL from the Original URL

Question

I have a table in my database which contains the URLs of some websites. I have to open those URLs and verify some links on those pages. The problem is that some URLs get red

Answer 1

This function will return the final destination of a link -- even if there are multiple redirects. It doesn't account for JavaScript-based redirects or META redirects. Notice that the previous solution didn't deal with Absolute & Relative URLs, since the LOCATION header could return something like "/newhome" you need to combine with the URL that served that response to identify the full URL destination.

    public static string GetFinalRedirect(string url)
    {
        if(string.IsNullOrWhiteSpace(url))
            return url;

        int maxRedirCount = 8;  // prevent infinite loops
        string newUrl = url;
        do
        {
            HttpWebRequest req = null;
            HttpWebResponse resp = null;
            try
            {
                req = (HttpWebRequest) HttpWebRequest.Create(url);
                req.Method = "HEAD";
                req.AllowAutoRedirect = false;
                resp = (HttpWebResponse)req.GetResponse();
                switch (resp.StatusCode)
                {
                    case HttpStatusCode.OK:
                        return newUrl;
                    case HttpStatusCode.Redirect:
                    case HttpStatusCode.MovedPermanently:
                    case HttpStatusCode.RedirectKeepVerb:
                    case HttpStatusCode.RedirectMethod:
                        newUrl = resp.Headers["Location"];
                        if (newUrl == null)
                            return url;

                        if (newUrl.IndexOf("://", System.StringComparison.Ordinal) == -1)
                        {
                            // Doesn't have a URL Schema, meaning it's a relative or absolute URL
                            Uri u = new Uri(new Uri(url), newUrl);
                            newUrl = u.ToString();
                        }
                        break;
                    default:
                        return newUrl;
                }
                url = newUrl;
            }
            catch (WebException)
            {
                // Return the last known good URL
                return newUrl;
            }
            catch (Exception ex)
            {
                return null;
            }
            finally
            {
                if (resp != null)
                    resp.Close();
            }
        } while (maxRedirCount-- > 0);

        return newUrl;
    }