您必须修改ItemsView以支持处理Rect的集合，而不是单个Rect：

• • 项目视图. cs**

public class ItemsView : Control
{
  public Item DataSource
  {
    get => (Item)GetValue(DataSourceProperty);
    set => SetValue(DataSourceProperty, value);
  }

  public static readonly DependencyProperty DataSourceProperty = DependencyProperty.Register(
    "DataSource",
    typeof(Item),
    typeof(ItemsView),
    new PropertyMetadata(default(Item), OnDataSourceChanged));

  private Panel ItemsHost { get; set; }
  private Dictionary<Rect, int> ContainerIndexTable { get; }
 
  static ItemsView() 
    => DefaultStyleKeyProperty.OverrideMetadata(typeof(ItemsView), new FrameworkPropertyMetadata(typeof(ItemsView)));

  public ItemsView() 
    => this.ContainerIndexTable = new Dictionary<Rect, int>();

  private static void OnDataSourceChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
  {
    var this_ = d as ItemsView;
    this_.UnloadRectangles(e.OldValue as Item);
    this_.LoadRectangles(e.NewValue as Item);
  }

  public override void OnApplyTemplate()
  {
    base.OnApplyTemplate();      
    this.ItemsHost = GetTemplateChild("PART_ItemsHost") as Panel;
    LoadRectangles(this.DataSource);
  }

  private void UnloadRectangles(Item item)
  {
    if (item is null
      || this.ItemsHost is null)
    {
      return;
    }

    foreach (Rect rectangleDefinition in item.ScaledRectangles)
    {
      if (this.ContainerIndexTable.TryGetValue(rectangleDefinition, out int containerIndex))
      {
        this.ItemsHost.Children.RemoveAt(containerIndex);
      }
    }
  }

  private void LoadRectangles(Item item)
  {
    if (item is null
      || this.ItemsHost is null)
    {
      return;
    }

    foreach (Rect rectangleDefinition in item.ScaledRectangles)
    {
      var container = new Rectangle()
      {
        Height = rectangleDefinition.Height,
        Width = rectangleDefinition.Width,
        Fill = new SolidColorBrush(item.ItemColor)
      };

      Canvas.SetLeft(container, rectangleDefinition.Left);
      Canvas.SetTop(container, rectangleDefinition.Top);

      int containerIndex = this.ItemsHost.Children.Add(container);
      _ = this.ContainerIndexTable.TryAdd(rectangleDefinition, containerIndex);
    }
  }
}

• • 德语. xaml**

<Style TargetType="local:ItemsView">
  <Setter Property="Template">
    <Setter.Value>
      <ControlTemplate TargetType="local:ItemsView">
        <Canvas x:Name="PART_ItemsHost" />
      </ControlTemplate>
    </Setter.Value>
  </Setter>
</Style>

• • 主窗口. xaml**

<ItemsControl>
  <ItemsControl.ItemTemplate>
    <DataTemplate DataType="{x:Type local:Item}">
      <local:ItemsView DataSource="{Binding}" />
    </DataTemplate>
  </ItemsControl.ItemTemplate>
</ItemsControl>