Why ComboBox sometimes cannot select a item?

[kyuranger]

The version of Avalonia I am using is the latest verion(11.1.4):

It works well when the model is string:

<UserControl xmlns="https://github.com/avaloniaui"
             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"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
			 xmlns:Local="using:AvaloniaApplication5"
			 xmlns:System="clr-namespace:System;assembly=System.Runtime"
			 x:DataType="Local:TestViewModel"
             x:Class="AvaloniaApplication5.MainView">	
	<Grid>
		<ScrollViewer>
			<ComboBox Grid.Row="1" ItemsSource="{Binding ItemOC}" SelectedItem="{Binding CurrentSelectedItem,Mode=TwoWay}">
				<ComboBox.ItemTemplate>
					<DataTemplate x:DataType="System:String">
						<TextBlock Text="{Binding }"></TextBlock>
					</DataTemplate>
				</ComboBox.ItemTemplate>
				<ComboBox.ItemsPanel>
					<ItemsPanelTemplate>
						<VirtualizingStackPanel />
					</ItemsPanelTemplate>
				</ComboBox.ItemsPanel>
			</ComboBox>
		</ScrollViewer>
	</Grid>
</UserControl>

using Avalonia;
using Avalonia.Controls;
using Avalonia.Data.Converters;
using Avalonia.Markup.Xaml;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Globalization;
using System;
using CommunityToolkit.Mvvm.ComponentModel;

namespace AvaloniaApplication5;

public partial class MainView : UserControl
{
    public MainView()
    {
        InitializeComponent();
        this.DataContext = new TestViewModel() { ItemOC = ["123","456","789"] };
    }
}
public partial class TestViewModel:ObservableObject
{
    [ObservableProperty]
    ObservableCollection<string> _ItemOC= new ObservableCollection<string>();

    [ObservableProperty]
    string _CurrentSelectedItem = "";
}

After I change the model a bit, sometimes the item cannot be select:

<UserControl xmlns="https://github.com/avaloniaui"
             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"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
			 xmlns:Local="using:AvaloniaApplication5"
			 xmlns:System="clr-namespace:System;assembly=System.Runtime"
			 x:DataType="Local:TestViewModel"
             x:Class="AvaloniaApplication5.MainView">	
	<Grid>
		<ScrollViewer>
			<ComboBox Grid.Row="1" ItemsSource="{Binding ItemOC}" SelectedItem="{Binding CurrentSelectedItem,Mode=TwoWay}">
				<ComboBox.ItemTemplate>
					<DataTemplate x:DataType="Local:ItemModel">
						<TextBlock>
							<Run Text="{Binding Code}"></Run>
							<Run Text="-"></Run>
							<Run Text="{Binding Name}"></Run>
						</TextBlock>
					</DataTemplate>
				</ComboBox.ItemTemplate>
				<ComboBox.ItemsPanel>
					<ItemsPanelTemplate>
						<VirtualizingStackPanel />
					</ItemsPanelTemplate>
				</ComboBox.ItemsPanel>
			</ComboBox>
		</ScrollViewer>
	</Grid>
</UserControl>

using Avalonia;
using Avalonia.Controls;
using Avalonia.Data.Converters;
using Avalonia.Markup.Xaml;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Globalization;
using System;
using CommunityToolkit.Mvvm.ComponentModel;

namespace AvaloniaApplication5;

public partial class MainView : UserControl
{
    public MainView()
    {
        InitializeComponent();
        this.DataContext = new TestViewModel() { ItemOC = [new ItemModel() {Name= "123",Code=0 }, new ItemModel() { Name = "456", Code = 1 }, new ItemModel() { Name = "789", Code = 2 }] };
    }
}
public partial class TestViewModel:ObservableObject
{
    [ObservableProperty]
    ObservableCollection<ItemModel> _ItemOC= new ObservableCollection<ItemModel>();

    [ObservableProperty]
    ItemModel _CurrentSelectedItem = new ItemModel();
}
public class ItemModel {
    public string Name { get; set; } = "";
    public int Code { get; set; } = 0;
}

What's wrong with my code?

[timunie]

CurrentSelectedItem should be available in the collection or your item model should override equals

[kyuranger]

I tried override Equals like this, but it doesn't work any:

public class ItemModel
{
    public string Name { get; set; } = "";
    public int Code { get; set; } = 0;
    public override bool Equals(object? obj)
    {
        if (obj is ItemModel _item)
        {
            if (_item.Code == this.Code && _item.Name == this.Name)
            {                    
                return true;
            }
        }                    
        return false;
    }
}