如何正确地将 IsPressed 属性绑定到我的命令参数？

我制作了一个自定义按钮来将命令绑定到（自定义，路由）IsPressedChanged事件，以便在按下按钮和释放按钮时执行该命令：

<local:CustomButton xmlns:i="http://schemas.microsoft.com/xaml/behaviors" x:Name="MyButton">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="CustomIsPressedChanged">
            <i:InvokeCommandAction Command="{Binding Path=SomeCommand}"/>
        </i:EventTrigger>
    </i:Interaction.Triggers>
</local:CustomButton>

使用自定义按钮实现：

public partial class CustomButton : Button
    {
        /* Register a custom routed event using the bubble routing strategy. */
        public static readonly RoutedEvent CustomIsPressedChangedEvent = EventManager.RegisterRoutedEvent(
            name: "CustomIsPressedChanged",
            routingStrategy: RoutingStrategy.Bubble,
            handlerType: typeof(RoutedEventHandler),
            ownerType: typeof(CustomButton));

        /* Provide CLR accessors for assigning an event handler. */
        public event RoutedEventHandler CustomIsPressedChanged
        {
            add { AddHandler(CustomIsPressedChangedEvent, value); }
            remove { RemoveHandler(CustomIsPressedChangedEvent, value); }
        }

        public CustomButton() { InitializeComponent(); }

        /* Custom Event handling of the IsPressedChanged event */
        protected override void OnIsPressedChanged(System.Windows.DependencyPropertyChangedEventArgs e)
        {
            /* Call the base class OnIsPressedChanged() method so IsPressedChanged event subscribers are notified. */
            base.OnIsPressedChanged(e);

            /* Raise custom event */
            RaiseEvent(new RoutedEventArgs(routedEvent: CustomIsPressedChangedEvent));
        }
    }

这完全符合预期。

现在问题来了：

当我尝试传播的价值IsPressed命令的属性如下所示：

<i:InvokeCommandAction Command="{Binding Path=SomeCommand}"
                       CommandParameter="{Binding ElementName=MyButton, Path=IsPressed}"/>

传播的值（看起来）总是旧值IsPressed。当我按下按钮时，调用的命令参数为 false，当我释放按钮时参数为 true。But当我检查的值IsPressed在事件处理程序内部CustomButton.OnIsPressedChanged()，它代表了预期的新值。

我的问题是：我该如何传播价值IsPressed得到正确的值？是否保证命令将始终使用旧值调用？在这种情况下，我可以简单地反转该值，但这对我来说似乎有点阴暗，我真的不想这样做，除非我知道它总是会产生正确的结果。

您可以通过DependencyPropertyChangedEventArgs作为参数RoutedEventArgs提出的：

protected override void OnIsPressedChanged(DependencyPropertyChangedEventArgs e)
{
    base.OnIsPressedChanged(e);

    // you may want to pass e.NewValue here for simplicity.
    RaiseEvent(new RoutedEventArgs(CustomIsPressedChangedEvent, e));
}

然后询问InvokeCommandAction将其传递给命令：

<i:InvokeCommandAction Command="{Binding Path=SomeCommand}"
                       PassEventArgsToCommand="True" />

然后，在命令中你just需要转换传递的对象以检索新值IsPressed:

SomeCommand = new ActionCommand(SomeCommandAction);

//...

private void SomeCommandAction(object o)
{
    if (o is not RoutedEventArgs routedEventArgs)
        return;

    if (routedEventArgs.OriginalSource is not DependencyPropertyChangedEventArgs eventArgs)
        return;

    if (eventArgs.NewValue is true)
        Count++;

    if (eventArgs.NewValue is false)
        Count--;

}

工作演示here https://github.com/Orace/SO/tree/main/SO_72230510.