System.Net.WebException was unhandled

[pucker22]

Hey guys I really need some help I have spent hours trying to fiddle this code,

I have this:-

 System.Net.WebClient client= new System.Net.WebClient();
 client.DownloadFile("http://localhost/test.txt", string.Concat("C:/test.txt"));

ok so that works fine, but I want it so that IF the file did not exist, it would have a message box poping up saying the file could not be found rather than getting a horrible message as such:-

The remote server returned an error. (404) Not Found.

I know the file doesnt' exist when I remove it from localhost, but I want to know how to verify whether or not the file exists befpre downloading, or something to give me the ability to handle custom errors!

Cheers in advance!