我不知道我的代码出了什么问题。我创建了自己的控制元素ControlA的示例（在代码中创建）。它有一个Data属性，包含一些结构。它显示部分数据，我想使用另一个自定义控件ControlB来显示数据的子集。但是，当我使用xaml中A组件的数据设置ControlB组件的属性时，它不会出现。
怎么了？
创建ControlA：

var controlA = new ControlA();
controlA.Data = new Tuple<string, string>("Some text data", "Some subset data");

_grid.Children.Add(controlA);

ControlA：

<?xml version="1.0" encoding="utf-8"?>
<UserControl
    x:Class="winui_3_app.components.ControlA"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:winui_3_app.components"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <StackPanel>
        <Grid Background="Aquamarine">
            <TextBlock Text="{Binding Data.Item1}" />
        </Grid>
        <Grid Background="Coral">
            <local:ControlB Text="{Binding Data.Item2}" />
        </Grid>
    </StackPanel>
</UserControl>

using System;
using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;

namespace winui_3_app.components;

public sealed partial class ControlA : UserControl
{
    public Tuple<string, string> Data
    {
        get => (Tuple<string, string>)GetValue(DataProperty);
        set => SetValue(DataProperty, value);
    }

    public static readonly DependencyProperty DataProperty = DependencyProperty.Register(nameof(Data), typeof(Tuple<string, string>), typeof(ControlA), new PropertyMetadata(null));

    public ControlA()
    {
        this.InitializeComponent();
        this.DataContext = this;
    }
}

ControlB：

<?xml version="1.0" encoding="utf-8"?>
<UserControl
    x:Class="winui_3_app.components.ControlB"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:winui_3_app.components"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">

    <Grid>
        <TextBlock Text="{Binding Text}" />
    </Grid>
</UserControl>

using Microsoft.UI.Xaml;
using Microsoft.UI.Xaml.Controls;

namespace winui_3_app.components;

public sealed partial class ControlB : UserControl
{
    public string Text
    {
        get => (string)GetValue(TextProperty);
        set => SetValue(TextProperty, value);
    }

    public static readonly DependencyProperty TextProperty = DependencyProperty.Register(nameof(Text), typeof(string), typeof(ControlB), new PropertyMetadata(string.Empty));

    public ControlB()
    {
        this.InitializeComponent();
        this.DataContext = this;
    }
}