WPF Window 自定义事件创建并绑定到 ICommand

Question

这是WPF/MVVM申请。 MainWindow.xaml.cs 后面的代码中有一些代码应该生成自定义事件，并且需要报告此事件的事实（可能带有参数）以查看模型 class (MainWindowViewModel.cs).

例如。我在 partial class MainWindow 中声明了 RoutedEvent TimerEvent 但我无法绑定到视图模型命令，因为此事件在 xaml 代码上不可用。错误：无法识别或无法访问计时器。

如何解决这个问题？谢谢！

 public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            var timer = new Timer();
            timer.Elapsed += new ElapsedEventHandler(OnTimedEvent);
            timer.Interval = 5000;
            timer.Enabled = true;
        }

        private void OnTimedEvent(object sender, ElapsedEventArgs e)
        {
            RaiseTimerEvent();
        }

        // Create a custom routed event
        public static readonly RoutedEvent TimerEvent = EventManager.RegisterRoutedEvent(
            "Timer", RoutingStrategy.Bubble, typeof(RoutedEventHandler), typeof(MainWindow));

        // Provide CLR accessors for the event
        public event RoutedEventHandler Timer
        {
            add => AddHandler(TimerEvent, value);
            remove => RemoveHandler(TimerEvent, value);
        }
        
        void RaiseTimerEvent()
        {
            var newEventArgs = new RoutedEventArgs(MainWindow.TimerEvent);
            RaiseEvent(newEventArgs);
        }
    }

<Window x:Class="CustomWindowEvent.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:CustomWindowEvent"
        Title="MainWindow" Height="250" Width="400"
        Timer="{Binding TimerCommand}">   // THIS PRODUCE ERROR Timer is not recognized or is not accessible.

    <Window.DataContext>
        <local:MainWindowViewModel/>
    </Window.DataContext>

    <Grid>
        <StackPanel>
            <TextBlock Text="{Binding Title}"/>
            <Button Width="75"
                    Height="24"
                    Content="Run"
                    Command="{Binding RunCommand}"/>
        </StackPanel>
    </Grid>
</Window>

Answer 1

您不能像这样将 ICommand 属性绑定到事件。

当您的 window 发出命令时，您可能会以编程方式调用命令：

void RaiseTimerEvent()
{
    var newEventArgs = new RoutedEventArgs(MainWindow.TimerEvent);
    RaiseEvent(newEventArgs);

    var vm = this.DataContext as MainWindowViewModel;
    if (vm != null)
        vm.TimerCommand.Execute(null);
}

另一种选择是使用 Microsoft.Xaml.Behaviors.Wpf 包中的 EventTrigger 和 InvokeCommandAction 来调用使用 XAML:

的命令

<Window .. xmlns:i="http://schemas.microsoft.com/xaml/behaviors">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="Timer" >
            <i:InvokeCommandAction Command="{Binding TimerCommand}" />
        </i:EventTrigger>
    </i:Interaction.Triggers>
</Window>

更多信息请参考this blog post。

WPF Window 自定义事件创建并绑定到 ICommand

WPF Window custom event creating and binding to ICommand

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