Wpf Combobox itemssource 绑定回调

Question

我有一个组合框，它绑定到视图模型列表属性。此列表属性然后调用数据层中的异步函数。

我想将组合框的选定索引属性设置为 "zero" 即选定索引=0;

实际情况是数据正在完美加载，但即使在我设置了选定索引后属性自异步调用以来它也没有应用。
属性绑定后有什么回调方法请告诉我

Answer 1

我做了一个示例应用程序

视图模型

class MainWindowViewModel : INotifyPropertyChanged
{

    public event PropertyChangedEventHandler PropertyChanged;

    private ObservableCollection<string> _source;
    private object _lock = new object();

    public IEnumerable<string> Source
    {
        get { return _source; }
    }

    public String SelectedItem { get; set; }
    public int SelectedIndex { get; set; }

    public MainWindowViewModel()
    {
        _source = new ObservableCollection<string>();
        BindingOperations.EnableCollectionSynchronization(_source, _lock);

        Task.Factory.StartNew(() => PopulateSourceAsunc());
    }

    private void PopulateSourceAsunc()
    {
        for (int i = 0; i < 10; i++)
        {
            _source.Add("Test " + i.ToString());
            Thread.Sleep(1000);
        }
        //SelectedItem = _source[6];
        SelectedIndex = 5;
        OnPropertyChanged("SelectedIndex");
    }

    [NotifyPropertyChangedInvocator]
    protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

Xaml

<StackPanel>
    <ComboBox ItemsSource="{Binding Source}"
              SelectedItem="{Binding SelectedItem}"
              SelectedIndex="{Binding SelectedIndex}">
        <ComboBox.ItemsPanel>
            <ItemsPanelTemplate>
                <VirtualizingStackPanel/>
            </ItemsPanelTemplate>
        </ComboBox.ItemsPanel>
    </ComboBox>
</StackPanel>

代码隐藏

    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = new MainWindowViewModel();
    }

BindingOperations class 在 System.Windows.Data

的命名空间中

Wpf Combobox itemssource 绑定回调

WpfCombo box itemsource binding call back

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combobox