我最终想出了如何自己做到这一点。我在这里发布答案，以便其他人可以看到有效的解决方案，也许 WPF 专家会过来告诉我一个更好/更优雅的方法来做到这一点。
所以，答案最终是#2。暴露内部属性被证明是正确的答案。设置它实际上很容易......一旦你知道如何去做。没有太多完整的例子（我能找到），所以希望这个例子能帮助遇到这个问题的其他人。
ComboBoxWithLabel.xaml.cs
此文件中重要的一点是 DependencyProperties 的使用。请注意，我们现在所做的只是公开属性（LabelContent 和ItemsSource）。 XAML 将负责将内部控件的属性连接到这些外部属性。
namespace BoundComboBoxExample
{
/// <summary>
/// Interaction logic for ComboBoxWithLabel.xaml
/// </summary>
public partial class ComboBoxWithLabel : UserControl
{
// Declare ItemsSource and Register as an Owner of ComboBox.ItemsSource
// the ComboBoxWithLabel.xaml will bind the ComboBox.ItemsSource to this
// property
public IEnumerable ItemsSource
{
get { return (IEnumerable)GetValue(ItemsSourceProperty); }
set { SetValue(ItemsSourceProperty, value); }
}
public static readonly DependencyProperty ItemsSourceProperty =
ComboBox.ItemsSourceProperty.AddOwner(typeof(ComboBoxWithLabel));
// Declare a new LabelContent property that can be bound as well
// The ComboBoxWithLable.xaml will bind the Label's content to this
public string LabelContent
{
get { return (string)GetValue(LabelContentProperty); }
set { SetValue(LabelContentProperty, value); }
}
public static readonly DependencyProperty LabelContentProperty =
DependencyProperty.Register("LabelContent", typeof(string), typeof(ComboBoxWithLabel));
public ComboBoxWithLabel()
{
InitializeComponent();
}
}
}
ComboBoxWithLabel.xaml
XAML 非常简单，除了 Label 和 ComboBox ItemsSource 上的绑定。我发现让这些绑定正确的最简单方法是在 .cs 文件中声明属性（如上），然后使用 VS2010 设计器从属性窗格设置绑定源。本质上，这是我所知道的将内部控件的属性绑定到基本控件的唯一方法。如果有更好的方法，请告诉我。
<UserControl x:Class="BoundComboBoxExample.ComboBoxWithLabel"
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:DesignHeight="28" d:DesignWidth="453" xmlns:my="clr-namespace:BoundComboBoxExample">
<Grid>
<DockPanel LastChildFill="True">
<!-- This will bind the Content property on the label to the 'LabelContent'
property on this control-->
<Label Content="{Binding Path=LabelContent,
RelativeSource={RelativeSource FindAncestor,
AncestorType=my:ComboBoxWithLabel,
AncestorLevel=1}}"
Width="100"
HorizontalAlignment="Left"/>
<!-- This will bind the ItemsSource of the ComboBox to this
control's ItemsSource property -->
<ComboBox ItemsSource="{Binding RelativeSource={RelativeSource FindAncestor,
AncestorType=my:ComboBoxWithLabel,
AncestorLevel=1},
Path=ItemsSource}"></ComboBox>
<!-- you can do the same thing with SelectedValuePath,
DisplayMemberPath, etc, but this illustrates the technique -->
</DockPanel>
</Grid>
</UserControl>
MainWindow.xaml
使用它的 XAML 一点也不有趣。这正是我想要的。您可以通过所有标准 WPF 技术设置ItemsSource 和LabelContent。
<Window x:Class="BoundComboBoxExample.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="86" Width="464" xmlns:my="clr-namespace:BoundComboBoxExample"
Loaded="Window_Loaded">
<Window.Resources>
<ObjectDataProvider x:Key="LookupValues" />
</Window.Resources>
<Grid>
<my:ComboBoxWithLabel LabelContent="Foo"
ItemsSource="{Binding Source={StaticResource LookupValues}}"
HorizontalAlignment="Left"
Margin="12,12,0,0"
x:Name="comboBoxWithLabel1"
VerticalAlignment="Top"
Height="23"
Width="418" />
</Grid>
</Window>
为了完整起见，这里是 MainWindow.xaml.cs
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}
private void Window_Loaded(object sender, RoutedEventArgs e)
{
((ObjectDataProvider)FindResource("LookupValues")).ObjectInstance =
(from i in Enumerable.Range(0, 5)
select string.Format("Bar {0}", i)).ToArray();
}
}