Achieve “slide down” animation in WPF

Question

I am attempting to create my own template for an Expander control. When the control is expanded, I want the content to slide down slowly.

The desired he

Answer 1

This is kind of an old question but I had problems with this today, so I guess posting my solution would be worth it:

I had to animate the Height property of a grid row (sliding up and down), but needed dynamic binding so that the row would slide again to the same position as before.

I found this answer to be very helpful (after fruitlessly battling XAML): http://go4answers.webhost4life.com/Question/found-solution-work-protected-override-190845.aspx

Sometimes doing things in the code-behind is just simpler:

        Storyboard sb = new Storyboard();

        var animation = new GridLengthAnimation
        {
                Duration = new Duration(500.Milliseconds()),
                From = this.myGridRow.Height,
                To = new GridLength(IsGridRowVisible ? GridRowPreviousHeight : 0, GridUnitType.Pixel)
        };

        // Set the target of the animation
        Storyboard.SetTarget(animation, this.myGridRow);
        Storyboard.SetTargetProperty(animation, new PropertyPath("Height"));

        // Kick the animation off
        sb.Children.Add(animation);
        sb.Begin();

The GridLengthAnimation class can be found here: http://social.msdn.microsoft.com/forums/en-US/wpf/thread/da47a4b8-4d39-4d6e-a570-7dbe51a842e4/