通过绑定隐藏 WPF 扩展器上的切换按钮

Question

我正在尝试使用我的 ViewModel 上设置为 Visibility 属性的属性动态隐藏扩展器上的切换按钮。至少这是我的想法。有没有办法只更改 ToggleButton 控件上的一个设置，而不必在我的 xaml 中执行 Toggle Button 的整个模板？

Answer 1

您可以为Expander 使用Loaded 事件并在事件处理程序中设置Binding，或者如果您想要一种无需代码的可重用方式，您可以使用附加行为。

附加行为在Template 中找到ToggleButton，并将Binding 设置为附加属性ToggleButtonVisibility。

在此处上传了一个示例应用程序：ExpanderToggleButtonVisibilityTest.zip

这样使用

<Expander Name="expander"
          behaviors:ExpanderBehavior.BindToggleButtonVisibility="True"
          behaviors:ExpanderBehavior.ToggleButtonVisibility="{Binding YourVisibilityProperty}"
          .../>

ExpanderBehavior

public class ExpanderBehavior
{
    public static DependencyProperty BindToggleButtonVisibilityProperty =
        DependencyProperty.RegisterAttached("BindToggleButtonVisibility",
                                            typeof(bool),
                                            typeof(ExpanderBehavior),
                                            new PropertyMetadata(false, OnBindToggleButtonVisibilityChanged));

    public static bool GetBindToggleButtonVisibility(Expander expander)
    {
        return (bool)expander.GetValue(BindToggleButtonVisibilityProperty);
    }
    public static void SetBindToggleButtonVisibility(Expander expander, bool value)
    {
        expander.SetValue(BindToggleButtonVisibilityProperty, value);
    }

    private static void OnBindToggleButtonVisibilityChanged(DependencyObject target, DependencyPropertyChangedEventArgs e)
    {
        Expander expander = target as Expander;
        if (expander.IsLoaded == true)
        {
            BindToggleButtonVisibility(expander);
        }
        else
        {
            RoutedEventHandler loadedEventHandler = null;
            loadedEventHandler = new RoutedEventHandler(delegate
            {
                BindToggleButtonVisibility(expander);
                expander.Loaded -= loadedEventHandler;
            });
            expander.Loaded += loadedEventHandler;
        }
    }

    private static void BindToggleButtonVisibility(Expander expander)
    {
        ToggleButton headerSite = expander.Template.FindName("HeaderSite", expander) as ToggleButton;
        if (headerSite != null)
        {
            Binding visibilityBinding = new Binding
            {
                Source = expander,
                Path = new PropertyPath(ToggleButtonVisibilityProperty)
            };
            headerSite.SetBinding(ToggleButton.VisibilityProperty, visibilityBinding);
        }
    }

    #region ToggleButtonVisibilityProperty

    public static DependencyProperty ToggleButtonVisibilityProperty = 
        DependencyProperty.RegisterAttached("ToggleButtonVisibility",
                                            typeof(Visibility),
                                            typeof(ExpanderBehavior),
                                            new PropertyMetadata(Visibility.Visible));

    public static Visibility GetToggleButtonVisibility(Expander expander)
    {
        return (Visibility)expander.GetValue(ToggleButtonVisibilityProperty);
    }
    public static void SetToggleButtonVisibility(Expander expander, Visibility value)
    {
        expander.SetValue(ToggleButtonVisibilityProperty, value);
    }

    #endregion // ToggleButtonVisibilityProperty
}