How to UpdateLayout of StackPanel?

Question

The problem is, if you click the button and expand the phone number, the stackpanel & border expand, which is great, but if you collapse it, the stackpanel & border do not collapse.

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525"
        Background="White"
        >
    <StackPanel>
        <Border BorderBrush="Black" BorderThickness="1">
            <ListBox x:Name="myListBox">
                <ListBox.ItemTemplate>
                    <DataTemplate>
                        <StackPanel Background="LightBlue" >
                            <StackPanel Orientation="Horizontal">
                                <TextBlock Text="John Smith"/>
                                <Button Click="Button_Click" Width="25" Height="25"/>
                            </StackPanel>
                            <StackPanel x:Name="PhoneNumber" Visibility="Collapsed">
                                <TextBlock Text="12345"/>
                            </StackPanel>
                        </StackPanel>
                    </DataTemplate>
                </ListBox.ItemTemplate>
            </ListBox>
        </Border>
    </StackPanel>
</Window>

With the following code-behind:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace WpfApplication1
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            myListBox.ItemsSource = new List<int>() { 1, 2 }; //add 2 elements; 
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            Button btn = sender as Button;

            StackPanel sp1 = VisualTreeHelper.GetParent(btn) as StackPanel;
            StackPanel sp2 = VisualTreeHelper.GetParent(sp1) as StackPanel;

            StackPanel phone = sp2.FindName("PhoneNumber") as StackPanel;

            if (phone.Visibility == System.Windows.Visibility.Collapsed)
                phone.Visibility = System.Windows.Visibility.Visible; 
            else
                phone.Visibility = System.Windows.Visibility.Collapsed;

            myListBox.UpdateLayout(); //these don't collapse my space
            this.UpdateLayout(); //these don't collapse my space
        }
    }
}

Answer 1

The issue is that the Listbox is using virtualization. If you disable that then the issue goes away, like so:

<ListBox x:Name="myListBox" BorderBrush="Black" BorderThickness="1">
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <StackPanel />
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
</ListBox>

Alternatively, you can leave the default ItemsPanel and set ScrollViewer.CanContentScroll="False" on the ListBox. Both disable virtualization though.

I believe this question is related.

Answer 2

Didn't dig to deep into this but it looks like you'll have to call InvalidateMeasure all the way up the chain to the ItemsPresenter (actually, the ItemsPanelTemplate). I'll update if I can up with something better

private void Button_Click(object sender, RoutedEventArgs e)
{
    Button btn = sender as Button;

    StackPanel sp1 = VisualTreeHelper.GetParent(btn) as StackPanel;
    StackPanel sp2 = VisualTreeHelper.GetParent(sp1) as StackPanel;

    StackPanel phone = sp2.FindName("PhoneNumber") as StackPanel;

    if (phone.Visibility == System.Windows.Visibility.Collapsed)
        phone.Visibility = System.Windows.Visibility.Visible; 
    else
        phone.Visibility = System.Windows.Visibility.Collapsed;

    DependencyObject dpObject = btn;
    while (dpObject != null)
    {
        if (dpObject is UIElement)
        {
            (dpObject as UIElement).InvalidateMeasure();
        }
        if (dpObject is ItemsPresenter)
            break;
        dpObject = VisualTreeHelper.GetParent(dpObject);
    }
}