Silverlgiht：快速去除/恢复对象的颜色

        private void btnTest_Click(object sender, RoutedEventArgs e)
        {
            SolidColorBrush brush = b.BorderBrush as SolidColorBrush;
            if (brush != null) 
            {
                Color c = brush.Color;
                if (c.A == 0)
                {
                    c.A = 0xff; //恢复颜色的Alpha分量
                }
                else 
                {
                    c.A = 0x00;//去除颜色的Alpha分量
                }              
                brush.Color = c;                
            }
        }