ok i have this code

here it is

Code:
void DownloadFileFromURL(string URL, string SaveFileName)
        {
            Uri u = new Uri(URL);
            Stream s = ((HttpWebRequest)HttpWebRequest.Create(u)).GetResponse().GetResponseStream();
            FileStream f = File.Create(SaveFileName);
            byte[] r = new byte[4096];
            while (true)
            {
                int num = s.Read(r, 0, 4096);
                if (num < 1)
                    break;
                f.Write(r, 0, num);
            }
        }
when i debug and i click the button it takes me to the code and it highlights this part of the code

Uri u = new Uri(URL);

please help me get this to work