The HttpWebRequest object makes it easy to check whether a web site is available or a URL is valid. Its HttpStatusCode property returns the status code from the request, which you can check to determine the site’s availability.

public static bool checkUrl(string url) {    bool rt = false;   if (url.StartsWith("www."))   {      url = "http://" + url;   }   HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(url);     HttpStatusCode code = new HttpStatusCode();     HttpWebResponse myResponse = null;    try    {        myResponse = (HttpWebResponse)myRequest.GetResponse();       code = myResponse.StatusCode;       rt = true;   }   catch(WebException err)   {       rt = false;   }    return rt;}

If the web site exists (the URL is valid) and running, the method returns true. If it doesn’t exist or isn’t available, the method will raise an exception, which gets trapped, and the method returns false.