private void AddLoader()
        {
            activityIndicatorView = (UIActivityIndicatorView)View.ViewWithTag(1000);

            // show busy indicator. create it first if it doesn't already exists
            if (activityIndicatorView == null)
            {
                var s = scrollView.Bounds;
                activityIndicatorView = new UIActivityIndicatorView()
                {
                    ActivityIndicatorViewStyle = UIActivityIndicatorViewStyle.Gray,
                    Tag = 1000
                };
                activityIndicatorView.BackgroundColor = UIColor.White;
                activityIndicatorView.Alpha           = 0.7f;
                scrollView.AddIfNotNull(activityIndicatorView);
                scrollView.AddConstraints(
                    activityIndicatorView.AtTopOf(scrollView),
                    activityIndicatorView.AtLeftOf(scrollView),
                    activityIndicatorView.AtRightOf(scrollView),
                    activityIndicatorView.AtBottomOf(scrollView)
                    );
                scrollView.BringSubviewToFront(activityIndicatorView);
                activityIndicatorView.StartAnimating();
            }
        }
 void AddIndicatorView()
 {
     _activityView                  = new UIActivityIndicatorView(UIActivityIndicatorViewStyle.WhiteLarge);
     _activityView.Alpha            = 0.5f;
     _activityView.HidesWhenStopped = true;
     _activityView.BackgroundColor  = UIColor.Black;
     View.AddIfNotNull(_activityView);
     View.AddConstraints(
         _activityView.AtTopOf(View),
         _activityView.AtLeftOf(View),
         _activityView.AtRightOf(View),
         _activityView.AtBottomOf(View)
         );
 }