Question

If it is only enlarge and shrink, it is easy.

private void button1_Click(object sender, RoutedEventArgs e)
{
    button1.BeginAnimation(Button.FontSizeProperty, new DoubleAnimation( 40,
                           new System.Windows.Duration(TimeSpan.FromSeconds(2)),
                               FillBehavior.Stop) { AutoReverse = true });
}

But now I hope when the font size grows to 40, stay for 2 seconds, then shrink. How to do this?

Answer 1

You can combine several animations into a StoryBoard, that should do the trick.
You can combine the following animations:

• One that enlarges the font size up to 40
• One that does nothing (with a duration of 2 sec)
• One that shrinks the font back