A Domain Name System (DNS) query may take up to 15 seconds to return or time out. If your request contains a host name that requires resolution and you set Timeout to a value less than 15 seconds, it may take 15 seconds or more before a WebException is thrown to indicate a time-out on your request.
// Create a Uri object.
Uri myUrl = new Uri ("file://" + fileName);
// Create a FileWebRequest object.
myFileWebRequest = (FileWebRequest)WebRequest.CreateDefault (myUrl);
// Set the time-out to the value selected by the user.
myFileWebRequest.Timeout = timeout;
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)