[Modify] Polish it

Author: sta

websocket-sharp/Net/HttpListenerResponse.cs

@@ -931,12 +931,22 @@ public void CopyFrom (HttpListenerResponse templateResponse)
  /// </exception>
  public void Redirect (string url)
  {
- checkDisposedOrHeadersSent ();
+ if (_disposed)
+ throw new ObjectDisposedException (GetType ().ToString ());
+
+ if (_headersSent) {
+ var msg = "The response is already being sent.";
+ throw new InvalidOperationException (msg);
+ }
+
  if (url == null)
  throw new ArgumentNullException ("url");
 
- Uri uri = null;
- if (!url.MaybeUri () || !Uri.TryCreate (url, UriKind.Absolute, out uri))
+ if (!url.MaybeUri ())
+ throw new ArgumentException ("Not an absolute URL.", "url");
+
+ Uri uri;
+ if (!Uri.TryCreate (url, UriKind.Absolute, out uri))
  throw new ArgumentException ("Not an absolute URL.", "url");
 
  _location = url;