WPF ComboBox 在是 DependencyObject 时不显示当前项目

Question

我的 XAML 中有这个非常简单的组合框:

<ComboBox Name="cmb1" Width="200" Height="23" ItemsSource="{Binding}" />

这是我背后的代码:

public class Test //: System.Windows.DependencyObject
{
    public string Name { get; set; }

    public override string ToString() { return Name; }
}

public MainWindow()
{
    InitializeComponent();

    var col = new ObservableCollection<Test>();
    cmb1.DataContext = col;
    col.Add(new Test { Name = "A" });
    col.Add(new Test { Name = "B" });
    col.Add(new Test { Name = "C" });
    col.Add(new Test { Name = "D" });
}

只要测试 类不是从 继承的依赖对象 一切安好。但是继承的时候，ComboBox 不展开时不显示当前项。
当我单击 ComboBox 并查看其下拉框时，选择了当前项目。

Answer 1

这是 karmicpuppet 的回答在一个现已删除的问题中:

This is interesting. Well, I've looked at the ComboBox class using Reflector and I see that in the ComboBox.UpdateSelectionBoxItems() method, part of it does something like:

If ItemTemplate, ItemTemplateSelector, and ItemStringFormat were not set, and selected item is a DependencyObject that is not derived from UIElement, call the ExtractString(selectedItem) method.

The ComboBox.ExtractString(dObj) method, on the other hand, apparently checks to see if the selectedItem (which is a DependencyObject) is either a TextBlock, a Visual, or a TextElement to display the appropriate string. Otherwise, it will return string.Empty.

所以最简单的解决方案是在组合框上设置它:

ItemStringFormat="{}{0}"