how to unblock website in c# window application

public bool unblockwebsite(string strurlunblock)
       {
           try
           {
               string tempFile = Path.GetTempFileName();
               string hostpath = Environment.GetEnvironmentVariable("windir") + "\\System32\\drivers\\etc\\hosts";
               using (StreamReader sr = new StreamReader(hostpath))
               {
                   using (StreamWriter sw = new StreamWriter(tempFile))
                   {
                       string line;

                       while ((line = sr.ReadLine()) != null)
                       {
                           if (line != " 127.0.0.1" + " " + strurlunblock)
                               sw.WriteLine(line);
                       }
                       sw.Close();
                   }
                   sr.Close();
               }

               //File.Delete(hostpath);
               //File.Move(tempFile, hostpath);

               if (File.Exists(tempFile))
                   File.Copy(tempFile, hostpath, true);
            return true;
           }
           catch
           {
               return false;
           }
       }