WPFToolkit AutoCompleteBox not binding correctly inside ListView

Question

After struggling a bit to just get started with WPFToolkit's AutoCompleteBox control, I'm facing another issue when trying to use an AutoCompleteBox inside a ListView, it almost binds perfectly but for a reason I ignore it doesn't show at first the ValueMemberPath and instead tries to convert the object to string which gives Namespace.object instead of the proper ValueMemberPath value, however when selecting another item in the AutoCompleteBox it works perfectly and it doesn't show any other Namespace.object.

Here's my code, you can just copy and paste it to get the same result (don't forget to add DotNetProjects.WpfToolkit.Input in NuGet Package Manager) :

• Namespace.MainWindow.xaml

<Window x:Class="Namespace.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:Namespace"
        mc:Ignorable="d"
        xmlns:toolkit="clr-namespace:System.Windows.Controls;assembly=DotNetProjects.Input.Toolkit"
        Title="AutoCompleteBox in ListView" Height="300" Width="350" WindowStartupLocation="CenterScreen">
    
    <!-- Required Template to show the names of the Items in the ItemsList -->
    <Window.Resources>
        <DataTemplate x:Key="AutoCompleteBoxItemTemplate">
            <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" Background="Transparent">
                <Label Content="{Binding Name}"/>
            </StackPanel>
        </DataTemplate>
    </Window.Resources>
    
    <StackPanel Margin="5">
        <StackPanel Orientation="Horizontal" Margin="0 5 0 0">
            <StackPanel Width="{Binding ElementName=FirstColumnWidth, Path=ActualWidth}">
                <TextBlock Text="ACB binded to Cart.Item"/>
                
                <!-- ACB that binds correctly -->
                <toolkit:AutoCompleteBox 
                                  ItemsSource="{Binding Path=ItemsList}"
                                   ValueMemberPath="Name"
                                   SelectedItem="{Binding Path=Cart.Item, Mode=TwoWay}"
                                   ItemTemplate="{StaticResource AutoCompleteBoxItemTemplate}"/>
            </StackPanel>

            <StackPanel Margin="15 0 0 0">
                <TextBlock Text="Value of Cart.Item.Name"/>
                <TextBlock Text="{Binding Path=Cart.Item.Name}"/>
            </StackPanel>
        </StackPanel>

        <TextBlock Margin="0 30 0 0" HorizontalAlignment="Center" Text="ListView with CartsList as ItemsListSource"/>
        <ListView ItemsSource="{Binding CartsList}">
            <ListView.View>
                <GridView>
                    <GridViewColumn x:Name="FirstColumnWidth">
                        <GridViewColumn.Header>
                            <TextBlock Text="ACB binded to each Cart.Item"/>
                        </GridViewColumn.Header>
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <!-- ACB that doesn't bind correctly -->
                                <toolkit:AutoCompleteBox
                                  ItemsSource="{
                                        Binding RelativeSource={RelativeSource AncestorType=Window},
                                        Path=DataContext.ItemsList}"
                                   ValueMemberPath="Name"
                                   SelectedItem="{Binding Path=Item, Mode=TwoWay}"
                                   ItemTemplate="{StaticResource AutoCompleteBoxItemTemplate}"/>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>

                    <GridViewColumn >
                        <GridViewColumn.Header>
                            <TextBlock Text="Value of each Cart.Item.Name"/>
                        </GridViewColumn.Header>
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <TextBlock Text="{Binding Path=Item.Name}"/>
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                </GridView>
            </ListView.View>
        </ListView>
    </StackPanel>
</Window>

• Code-Behind (MainWindow.xaml.cs)

using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;

namespace Namespace
{
    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        // INPC Implementation
        public event PropertyChangedEventHandler PropertyChanged;
        private void OnPropertyChanged([CallerMemberName] string propertyName = null)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        // The list that contains Items that will be chosen in a Cart
        private ObservableCollection<Item> _ItemsList;
        public ObservableCollection<Item> ItemsList
        {
            get => _ItemsList;
            set
            {
                _ItemsList = value;
                OnPropertyChanged();
            }
        }

        // The list that contains Carts that will be shown in the ListView
        private ObservableCollection<Cart> _CartsList;
        public ObservableCollection<Cart> CartsList
        {
            get => _CartsList;
            set
            {
                _CartsList = value;
                OnPropertyChanged();
            }
        }

        // A signle Cart
        private Cart _Cart;
        public Cart Cart
        {
            get => _Cart;
            set
            {
                _Cart = value;
                OnPropertyChanged();
            }
        }

        public MainWindow()
        {
            DataContext = this;
            InitializeComponent();

            // Populating ItemsList
            ItemsList = new ObservableCollection<Item>()
            {
                new Item("T-shirt"), new Item("Jeans"), new Item("Boots"),
            };

            // Populating CartsList
            CartsList = new ObservableCollection<Cart>()
            {
                new Cart(ItemsList[0]),
                new Cart(ItemsList[2]),
                new Cart(ItemsList[1]),
                new Cart(ItemsList[0]),
                new Cart(ItemsList[1]),
            };

            // Setting an Item to Cart
            Cart = new Cart(ItemsList[2]);

        }
    }

    // Cart Object
    public class Cart
    {
        public Item Item { get; set; }

        public Cart(Item item) => Item = item;
    }

    // Item Object
    public class Item
    {
        // Important to be private set so it cannot be changed
        public string Name { get; private set; }

        public Item(string name) => Name = name;
    }
}

Answer 1

For some reason the selection change that updates the text according to the ValueMemberPath is not triggered when nesting the AutoCompleteBox in the ListView. The SelectionChanged event does not even fire. I could not figure out why exactly and if this is a bug or not. However, I can show you a workaround using the Microsoft.Xaml.Behaviors.Wpf package.

You can create a trigger action that resets the SelectedItem and assigns it again on AutoCompleteBox.

public class ForceUpdateSelectedItemAction : TriggerAction<AutoCompleteBox>
{
   protected override void Invoke(object parameter)
   {
      var selectedItem = AssociatedObject.SelectedItem;
      AssociatedObject.SetCurrentValue(AutoCompleteBox.SelectedItemProperty, null);
      AssociatedObject.SetCurrentValue(AutoCompleteBox.SelectedItemProperty, selectedItem);
   }
}

This trigger action can be used for the Loaded event of the AutoCompleteBox.

<toolkit:AutoCompleteBox ...>
   <b:Interaction.Triggers>
      <b:EventTrigger EventName="Loaded">
         <local:ForceUpdateSelectedItemAction/>
      </b:EventTrigger>
   </b:Interaction.Triggers>
</toolkit:AutoCompleteBox>

This will cause an update of the selection and the text without changing the bound property.