Usercontrol未在设计器

Question

我有自定义用户控件：

<UserControl Name="ddTextBox" x:Class="UserControlsLibrary.DDTextBox"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             mc:Ignorable="d" 
             d:DesignWidth="250" FontFamily="Tahoma" FontSize="14" MinHeight="25" Height="275">
    <StackPanel>
        <TextBox Name="ControlText" Height="25"  HorizontalAlignment="Stretch" VerticalAlignment="Top" Text="{Binding Path=Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"/>
        <ListBox Name="ControlList" VerticalAlignment="Top" MaxHeight="250"  HorizontalAlignment="Stretch" Visibility="Collapsed" ItemsSource="{Binding Path=DList, UpdateSourceTrigger=PropertyChanged}">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Vertical">
                        <TextBlock Text="{Binding}"/>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </StackPanel>
</UserControl>

后面的代码：

using System;
using System.Collections;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Input;

namespace UserControlsLibrary
{
  public partial class DDTextBox : UserControl, INotifyPropertyChanged
  {
    private string _text;
    public string Text { get => _text ?? string.Empty; set { _text = value; OnPropertyChanged(); } }

    public DDTextBox()
    {
      InitializeComponent();
      ControlText.DataContext = this;
      ControlList.DataContext = this;
      ControlText.TextChanged += TextChanged;
      ControlText.GotKeyboardFocus += KeyboardFocusChanged;
      ControlText.LostKeyboardFocus += KeyboardFocusChanged;
      ControlList.SelectionChanged += SelectionChanged;
      ControlList.GotKeyboardFocus += KeyboardFocusChanged;
      ControlList.LostKeyboardFocus += KeyboardFocusChanged;
      IsKeyboardFocusWithinChanged += DDTextBox_IsKeyboardFocusWithinChanged;
    }

    private void TextChanged(object sender, TextChangedEventArgs e)
    { DItemsSource = ItemsSource.Cast<string>().ToList().FindAll(r => r.IndexOf(( (TextBox)sender ).Text, StringComparison.OrdinalIgnoreCase) >= 0); }

    private void SelectionChanged(object sender, SelectionChangedEventArgs e)
    { Text = ( e.AddedItems.Count > 0 ) ? e.AddedItems[0].ToString() : string.Empty; ( (ListBox)sender ).Visibility = Visibility.Collapsed; }

    private void KeyboardFocusChanged(object sender, KeyboardFocusChangedEventArgs e)
    {
      ControlList.Visibility = ( e.NewFocus == ControlList || e.NewFocus == ControlText ) ? Visibility.Visible : Visibility.Collapsed;
      if ( e.OldFocus?.GetType() == typeof(ListBox) ) ( (ListBox)e.OldFocus ).SelectedIndex = -1;
    }

    private void DDTextBox_IsKeyboardFocusWithinChanged(object sender, DependencyPropertyChangedEventArgs e)
    {
      if ( (bool)e.OldValue == true && (bool)e.NewValue == false )
      { RaiseEvent(new RoutedEventArgs(UserControlLostFocusEvent, this)); }
    }

    private void ControlLostFocus(object sender, RoutedEventArgs e)
    { if ( !ControlList.IsFocused && !ControlText.IsFocused ) { ControlList.Visibility = Visibility.Collapsed; ControlList.SelectedIndex = -1; } }

    public event RoutedEventHandler UserControlLostFocus
    {
      add { AddHandler(UserControlLostFocusEvent, value); }
      remove { RemoveHandler(UserControlLostFocusEvent, value); }
    }

    public IEnumerable ItemsSource
    {
      private get { return (IEnumerable)GetValue(ItemsSourceProperty); }
      set { SetValue(ItemsSourceProperty, value); SetValue(DItemsSourceProperty, value); }
    }

    /// <summary>
    /// Dynamically generated ItemsSource based on Text property. Changes made to this may be lost. List changes should be made to the ItemsSource.
    /// </summary>
    public IEnumerable DItemsSource
    {
      private get { return (IEnumerable)GetValue(DItemsSourceProperty); }
      set { SetValue(DItemsSourceProperty, value); }
    }

    public static DependencyProperty DItemsSourceProperty => dItemsSourceProperty;

    public static DependencyProperty ItemsSourceProperty => itemsSourceProperty;

    public static RoutedEvent UserControlLostFocusEvent => userControlLostFocusEvent;

    private static readonly DependencyProperty itemsSourceProperty = DependencyProperty.Register("ItemsSource", typeof(IEnumerable), typeof(DDTextBox), new PropertyMetadata(new PropertyChangedCallback(OnItemsSourcePropertyChanged)));

    private static readonly DependencyProperty dItemsSourceProperty = DependencyProperty.Register("DItemsSource", typeof(IEnumerable), typeof(DDTextBox), new PropertyMetadata(new PropertyChangedCallback(OnItemsSourcePropertyChanged)));

    private static readonly RoutedEvent userControlLostFocusEvent = EventManager.RegisterRoutedEvent("UserControlLostFocus", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(DDTextBox));

    private static void OnItemsSourcePropertyChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
    { if ( sender is DDTextBox control ) control.OnItemsSourceChanged((IEnumerable)e.NewValue, (IEnumerable)e.OldValue); }

    private void OnItemsSourceChanged(IEnumerable newValue, IEnumerable oldValue)
    {
      if ( oldValue is INotifyCollectionChanged oldValueINotifyCollectionChanged )
      { oldValueINotifyCollectionChanged.CollectionChanged -= new NotifyCollectionChangedEventHandler(NewValueINotifyCollectionChanged_CollectionChanged); }
      if ( newValue is INotifyCollectionChanged newValueINotifyCollectionChanged )
      { newValueINotifyCollectionChanged.CollectionChanged += new NotifyCollectionChangedEventHandler(NewValueINotifyCollectionChanged_CollectionChanged); }
    }

    void NewValueINotifyCollectionChanged_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)    { }

    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged([CallerMemberName] string Name = "")
    { PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(Name)); }
  }
}

在我的主项目中引用并添加到主窗口：

<Window Name="Main" x:Class="POSystem.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:myCtrls="clr-namespace:UserControlsLibrary;assembly=UserControlsLibrary"
        Title="Purchase Order" Height="850" Width="1100" Background="#FFD8D0A9">
    <Grid Name="TheGrid" Focusable="True" MouseDown="ClearFocus_OnClick" Background="Transparent">
        <myCtrls:DDTextBox x:Name="ItemsBox" Width="300" VerticalAlignment="Top" HorizontalAlignment="Left" Panel.ZIndex="1"/>
    </Grid>
</Window>

在运行时，所有内容都会显示并按原样运行，但是，在主页面的窗口设计器中，除了指示控件在那里的轮廓之外，它不会显示任何内容。此轮廓可以从该位置的单个行（仅所有功能正常工作）或如果我添加最小或仅直线高度，它显示控件的空轮廓。如何在主窗口设计器的用户控件中显示（应该是）可见的文本框？