如何在UserControl中填充StackPanel？

<UserControl>
    <StackPanel>
        <!-- 添加内容 -->
    </StackPanel>
</UserControl>

<UserControl>
    <StackPanel x:Name="MyStackPanel"/>
</UserControl>

public partial class MyUserControl : UserControl
{
    public MyUserControl()
    {
        InitializeComponent();
        // 动态添加内容
        Button button = new Button();
        button.Content = "Click me!";
        MyStackPanel.Children.Add(button);
    }
}

<UserControl>
    <StackPanel ItemsSource="{Binding MyItems}">
        <StackPanel.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding}" />
            </DataTemplate>
        </StackPanel.ItemTemplate>
    </StackPanel>
</UserControl>

public partial class MyUserControl : UserControl
{
    public MyUserControl()
    {
        InitializeComponent();
        // 设置数据上下文
        DataContext = new MyViewModel();
    }
}

public class MyViewModel : INotifyPropertyChanged
{
    private ObservableCollection<string> _myItems;
    public ObservableCollection<string> MyItems
    {
        get { return _myItems; }
        set
        {
            _myItems = value;
            OnPropertyChanged(nameof(MyItems));
        }
    }

    // INotifyPropertyChanged的实现...
}