ListView in WinUI maintains ListBox text after reset-CodePudding

I have a ListView in a WinUI 3 app (target framework net6.0-windows10.0.19041.0) with a data template that contains a TextBox. The ItemsSource is bound to an ObservableCollection in the code-behind file. There is also a button after the list to clear the collection and add a new item.

I noticed a strange behaviour: if i write anything in the TextBox, that text is retained after i click the Clear button. I would expect it to insert a completely new TextBox in the ListView, with no text in it.

Why does this happen? Does it have something to do with virtualization?

Here is the xaml file:

<Window
    x:Class="WinUISample.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:WinUISample"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <StackPanel HorizontalAlignment="Center" VerticalAlignment="Center">
        <ListView ItemsSource="{x:Bind _items }" >
            <ListView.ItemTemplate>
                <DataTemplate x:DataType="x:String">
                    <TextBox Width="250" /> <!-- intentionally empty -->
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>

        <Button Click="myButton_Click">Clear</Button>
    </StackPanel>
</Window>

And this is the code-behind file:

using Microsoft.UI.Xaml;
using System.Collections.ObjectModel;

namespace WinUISample
{
    public sealed partial class MainWindow : Window
    {
        private readonly ObservableCollection<string> _items;

        public MainWindow()
        {
            InitializeComponent();

            _items = new ObservableCollection<string>(new[]
            {
                "1"
            });
        }

        private void myButton_Click(object sender, RoutedEventArgs e)
        {
            _items.Clear();
            _items.Add("1");
        }
    }
}

CodePudding user response：

This should be because of its Virtualization feature. Since you are not binding your Text, you'll get the same text.

You can avoid this behavior by binding your Text,

<TextBox Width="250" Text="{x:Bind}" />

or by changing the ItemsPanel.

<ListView ItemsSource="{x:Bind _items}" >
    <!--<ListView.ItemsPanel>
        <ItemsPanelTemplate>
            <StackPanel/>
        </ItemsPanelTemplate>
    </ListView.ItemsPanel>-->
    <ListView.ItemTemplate>
        <DataTemplate x:DataType="x:String">
            <TextBox Width="250" />
            <!-- intentionally empty -->
        </DataTemplate>
    </ListView.ItemTemplate>
</ListView>