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天儿真好!

我希望我的WPF ComboBox在其数据绑定选择时显示一些替代文本null.

视图模型具有预期的属性:

public ThingoSelectionViewModel : INotifyPropertyChanged {
    public ThingoSelectionViewModel(IProvideThingos) {
        this.Thingos = IProvideThingos.GetThingos();
    }

    public ObservableCollection<Thingo> Thingos { get; set; }

    public Thingo SelectedThingo { 
        get { return this.selectedThingo; }
        set { // set this.selectedThingo and raise the property change notification
    }

    // ...

}

该视图以预期的方式将XAML绑定到视图模型:

<ComboBox x:Name="ComboboxDrive" SelectedItem="{Binding Path=SelectedThingo}"
          IsEditable="false" HorizontalAlignment="Left" MinWidth="100" 
          IsReadOnly="false" Style="{StaticResource ComboboxStyle}"
          Grid.Column="1" Grid.Row="1" Margin="5" SelectedIndex="0">
    <ComboBox.ItemsSource>
        <CompositeCollection>
        <ComboBoxItem IsEnabled="False">Select a thingo</ComboBoxItem>
        <CollectionContainer 
            Collection="{Binding Source={StaticResource Thingos}}" />
        </CompositeCollection>
    </ComboBox.ItemsSource>
</ComboBox>

该 …