Question

我有自定义依赖属性的用户控件...

public static readonly DependencyProperty ImageKeyProperty =
            DependencyProperty.Register("ImageKey", typeof(string), typeof(ImageSelector),
                 new FrameworkPropertyMetadata(null,
                        FrameworkPropertyMetadataOptions.BindsTwoWayByDefault,
                        OnImageKeyPropertyChanged));

public string ImageKey
{
    get { return (string)GetValue(ImageKeyProperty); }
    set { SetValue(ImageKeyProperty, value); }
}


private static void OnImageKeyPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        ImageSelector imageSelector = d as ImageSelector;
        if (imageSelector == null) return;

        if (e.NewValue == null || e.NewValue.ToString() == "")
        {
            imageSelector.Image.Source = null;
            imageSelector.buttonSelect.Content = "select...";
            imageSelector.Image.Visibility = Visibility.Collapsed;
        }
        else
        {
            imageSelector.Image.Source = ImageLibrary.GetImage(e.NewValue.ToString());
            imageSelector.buttonSelect.Content = "change...";
            imageSelector.Image.Visibility = Visibility.Visible;
        }

        imageSelector.PropertyChanged?.Invoke(imageSelector, new PropertyChangedEventArgs("ImageKey"));
    }

private void Button_Click(object sender, RoutedEventArgs e)
    {
        ImageSelectWindow w = new ImageSelectWindow();
        w.ShowDialog();
        if (w.DialogResult.HasValue && w.DialogResult.Value)
        {
            this.ImageKey = w.SelectedImageKey;
        }
    }

如果我将ViewModel（即DataContext）绑定到它......

<myControl ImageKey={Binding Image} />

我是否应该能够以编程方式在自定义UserControl中设置ImageKey值并使绑定的ViewModel属性更新？显然不是，因为它不起作用。

我错过了什么？！？！？

Answer 1

“我不能以编程方式设置ImageKey值吗？”

简短的回答：嗯...不。抱歉，这已经很久了，但是以防万一有人发现它并感到奇怪。

您在这里绑定：

<myControl ImageKey={Binding Image} />

在这里，您正在破坏绑定：

this.ImageKey = w.SelectedImageKey;

总之，不，您不能以编程方式更新绑定属性。而是更新其绑定值：

(this.DataContext as MyViewModel).Image = w.SelectedImageKey;

玩得开心。

更新DependencyProperty值而不更新绑定的ViewModel

1 个答案: