problem checking for 404 [modified]

[C# Programming]

I am trying to write a web app that will check to see if a given URL is valid. This is the code i have so far:


WebRequest wr = WebRequest.Create(url);
wr.Method = WebRequestMethods.Http.Head;
try
{
using (HttpWebResponse response = (HttpWebResponse)wr.GetResponse())
{
Label1.Text = (response.StatusCode.ToString());
}
}

catch (Exception)
{
Label1.Text = ("Invalid URL");

}


It works for checking if http://www.google.com, Label1 reads "OK" after, and it also works with a non existent page, such as http://www.google.com/notapage, but I'm trying to check to see if, for example, "http://www.amazon.com/exec/obidos/ASIN/B000GELXHY" is a valid URL, and after the code is executed, Label1 reads "Invalid URL", even though this is a valid URL.

I am new to C#, so I may be using the wrong class for what I'm trying to do. Any help would be greatly appreciated.

P.S. I don't know if it's relevant, but the code is being executed upon a button click.
P.S.S. replace "url" above with whatever url i am currently testing

modified on Saturday, November 7, 2009 3:05 PM