<ItemsControl x:Class="HDSProject.Control.CustomFont" 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" xmlns:local="clr-namespace:HDSProject.Control" mc:Ignorable="d" d:DesignHeight="450" d:DesignWidth="800" x:Name="itemCtrl" ItemsSource="{Binding Path=Title2, RelativeSource={RelativeSource Mode=Self}}" FontSize="20" Foreground="Teal" > <ItemsControl.ItemsPanel> <ItemsPanelTemplate> <StackPanel Orientation="Horizontal"/> </ItemsPanelTemplate> </ItemsControl.ItemsPanel> <ItemsControl.ItemTemplate> <DataTemplate> <StackPanel> <Border Margin="{Binding Path=CharacterSpacing, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=local:CustomFont}}"> <TextBlock Text="{Binding}" /> </Border> <Rectangle Height="1" Fill="{Binding Foreground, ElementName=itemCtrl}" Margin="0,0,0,5"> <Rectangle.Style> <Style TargetType="Rectangle"> <Setter Property="Visibility" Value="Collapsed" /> <Style.Triggers> <DataTrigger Binding="{Binding ShowUnderline, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=local:CustomFont}}" Value="True"> <Setter Property="Visibility" Value="Visible" /> </DataTrigger> </Style.Triggers> </Style> </Rectangle.Style> </Rectangle> </StackPanel> </DataTemplate> </ItemsControl.ItemTemplate> </ItemsControl>这是个自定控件，我在后台声明了一个Border对象，怎么让Border对象包裹这个控件

你可以在自定义控件的代码中找到ItemsControl，并将其包含在一个Border中，然后设置Border的边框、背景等属性，使其包裹住ItemsControl。具体代码如下：

public class CustomFont : Control
{
    private Border border;

    public CustomFont()
    {
        this.DefaultStyleKey = typeof(CustomFont);
    }

    public override void OnApplyTemplate()
    {
        base.OnApplyTemplate();

        // 找到ItemsControl
        var itemsControl = GetTemplateChild("itemCtrl") as ItemsControl;
        if (itemsControl != null)
        {
            // 创建一个Border
            border = new Border();
            // 把ItemsControl放入Border中
            border.Child = itemsControl;
            // 设置Border的边框、背景等属性
            border.BorderThickness = new Thickness(1);
            border.BorderBrush = Brushes.Black;
            border.Background = Brushes.White;
            // 将Border加入自定义控件的视觉树中
            this.AddVisualChild(border);
        }
    }

    protected override int VisualChildrenCount
    {
        get { return border != null ? 1 : 0; }
    }

    protected override Visual GetVisualChild(int index)
    {
        if (index == 0 && border != null)
        {
            return border;
        }
        else
        {
            throw new ArgumentOutOfRangeException("index");
        }
    }
}

这样就可以让Border对象包裹住CustomFont自定义控件了。需要注意的是，在自定义控件的代码中，我们需要重载VisualChildrenCount和GetVisualChild方法，以便正确地处理自定义控件的视觉树。