Expanders in Grid

Question

This is going to be straight forward no doubt, but for what ever reason, my mind is drawing a blank on it.

I\'ve got a small, non-resizeable window (325x450) which has 3

Answer 1

This requirement is a little unusal because the you want the state of the Children in the Grid to decide the Height of the RowDefinition they are in.
I really like the layout idea though and I can't believe I never had a similar requirement myself.. :)

For a reusable solution I would use an Attached Behavior for the Grid.
The behavior will subscribe to the Attached Events Expander.Expanded and Expander.Collapsed and in the event handlers, get the right RowDefinition from Grid.GetRow and update the Height accordingly. It works like this

And here is GridExpanderSizeBehavior

public class GridExpanderSizeBehavior
{
    public static DependencyProperty SizeRowsToExpanderStateProperty =
        DependencyProperty.RegisterAttached("SizeRowsToExpanderState",
                                            typeof(bool),
                                            typeof(GridExpanderSizeBehavior),
                                            new FrameworkPropertyMetadata(false, SizeRowsToExpanderStateChanged));
    public static void SetSizeRowsToExpanderState(Grid grid, bool value)
    {
        grid.SetValue(SizeRowsToExpanderStateProperty, value);
    }
    private static void SizeRowsToExpanderStateChanged(object target, DependencyPropertyChangedEventArgs e)
    {
        Grid grid = target as Grid;
        if (grid != null)
        {
            if ((bool)e.NewValue == true)
            {
                grid.AddHandler(Expander.ExpandedEvent, new RoutedEventHandler(Expander_Expanded));
                grid.AddHandler(Expander.CollapsedEvent, new RoutedEventHandler(Expander_Collapsed));
            }
            else if ((bool)e.OldValue == true)
            {
                grid.RemoveHandler(Expander.ExpandedEvent, new RoutedEventHandler(Expander_Expanded));
                grid.RemoveHandler(Expander.CollapsedEvent, new RoutedEventHandler(Expander_Collapsed));
            }
        }
    }
    private static void Expander_Expanded(object sender, RoutedEventArgs e)
    {
        Grid grid = sender as Grid;
        Expander expander = e.OriginalSource as Expander;
        int row = Grid.GetRow(expander);
        if (row <= grid.RowDefinitions.Count)
        {
            grid.RowDefinitions[row].Height = new GridLength(1.0, GridUnitType.Star); 
        }
    }
    private static void Expander_Collapsed(object sender, RoutedEventArgs e)
    {
        Grid grid = sender as Grid;
        Expander expander = e.OriginalSource as Expander;
        int row = Grid.GetRow(expander);
        if (row <= grid.RowDefinitions.Count)
        {
            grid.RowDefinitions[row].Height = new GridLength(1.0, GridUnitType.Auto);
        }
    }
}