你能在XAML中的数据绑定ItemsControl中添加一个额外的项吗？

   <ItemsControl.Items>
       <system:String>Item 1</system:String>
       <system:String>Item 2</system:String>
       <system:String>Item 3</system:String>
    </ItemsControl.Items>
   <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding}" />
        </DataTemplate>
    </ItemsControl.ItemTemplate>
   <system:String>Extra Item</system:String>
</ItemsControl>

   <ItemsControl.ItemsSource>
        <CompositeCollection>
           <CollectionContainer Collection="{Binding Items}" />
           <system:String>Extra Item</system:String>
        </CompositeCollection>
    </ItemsControl.ItemsSource>
   <ItemsControl.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding}" />
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>