private void FavoriteButton_Clicked(object sender, EventArgs e)
        {
            ImageButton button = (ImageButton)sender;

            Common.VideoViewModel vvm = (Common.VideoViewModel)button.Source.BindingContext;
            vvm.Favorite = vvm.Favorite ^ true;
            if (vvm.Favorite)
            {
                button.Source = tool.LIKEURL;
                database.addVideo(vvm);
            }
            else
            {
                button.Source = tool.DISLIKEURL;
                database.removeVideo(vvm);
            }
        }