The Content of the Item in the TreeView is displayed, but the Children content is not displayed！

[Linjie123]

Describe the bug

I wrote following the example of data binding for the TreeView control in a WinUI 3 application, and if I add a layout to Children, then the content of the treeviewitem is not displayed

The following is the page code

   <TreeView  x:Name="Tv_Channel" 
              Grid.Row="1"
              Margin="10"` 
              AllowDrop="True" 
              CanDragItems="True" 
              ItemInvoked="Tv_Channel_ItemInvoked" 
              ItemsSource="{Binding ChannelSource}">

             <TreeView.ItemTemplate>
               <DataTemplate x:DataType="channels:Channel">
                 <TreeViewItem Content="{Binding Layer}" ItemsSource="{Binding Children}">

                            <!--<TreeViewItem.Template>
                            <ControlTemplate>
                                <StackPanel HorizontalAlignment="Left"
                                            VerticalAlignment="Center"
                                            BorderBrush="Transparent"
                                            BorderThickness="1"
                                            Orientation="Vertical">
                                    <TextBlock FontSize="15"
                                               Foreground="White"
                                               Text="{Binding cName}" />
                                    <TextBlock FontSize="8"
                                               Text="{Binding cLink}"
                                               Visibility="Collapsed" />
                                </StackPanel>
                            </ControlTemplate>
                            </TreeViewItem.Template>-->

                  </TreeViewItem>
                </DataTemplate>
             </TreeView.ItemTemplate>       
    </TreeView>

Steps to reproduce the bug

1. Added a tree control to the page to use data binding operations
2. Add CS code to use ViewModel
3. Added some data in the viewmodel
4. Then run the program, and the content in the children is not displayed

Expected behavior

No response

Screenshots

NuGet package version

WinUI 3 - Windows App SDK 1.2.3: 1.2.230118.102

Windows version

Windows 11 (22H2): Build 22621

Additional context

public class VideoViewModel : ObservableObject
{
public ObservableCollection ChannelSource { get; set; }

    public VideoViewModel()
    {
        ChannelSource = new ObservableCollection<Channel>
        {
            new Channel
            {
                Layer = "央视节目",
                Children = new ObservableCollection<Channel>
                {
                    new Channel { cName = "CCTV-1综合", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225642/index.m3u8") },
                    new Channel { cName = "CCTV-2财经", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225643/index.m3u8") },
                    new Channel { cName = "CCTV-3综艺", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225634/index.m3u8") },
                    new Channel { cName = "CCTV-4国际", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225621/index.m3u8") },
                    new Channel { cName = "CCTV-5体育", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225633/index.m3u8") },
                    new Channel { cName = "CCTV-5+体育", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225706/index.m3u8") },
                    new Channel { cName = "CCTV-6电影", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225632/index.m3u8") },
                    new Channel { cName = "CCTV-7军事", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225644/index.m3u8") },
                    new Channel { cName = "CCTV-8电视剧", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225631/index.m3u8") },
                    new Channel { cName = "CCTV-9英语新闻", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225646/index.m3u8") },
                    new Channel { cName = "CCTV-10科教", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225636/index.m3u8") },
                    new Channel { cName = "CCTV-11戏曲", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225628/index.m3u8") },
                    new Channel { cName = "CCTV-12社会与法", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225637/index.m3u8") },
                    new Channel { cName = "CCTV-13新闻", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225638/index.m3u8") },
                    new Channel { cName = "CCTV-14少儿", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225640/index.m3u8") },
                    new Channel { cName = "CCTV-15音乐", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225641/index.m3u8") },
                    new Channel { cName = "CCTV-17农业", cLink = new Uri("http://39.134.115.163:8080/PLTV/88888910/224/3221225908/index.m3u8") },
                }
            },}; }}}