WPF MVVM取消Window.Closing事件 [英] WPF MVVM cancel Window.Closing event

问题描述

在WPF应用程序和MVVMLight Toolkit中，我想听听您的意见，如果需要取消Window Close事件，什么是实现的最佳方法? 在Window.Closing事件中，我可以设置e.Cancel = true，以防止关闭窗体.在ViewModel上下文中确定是否允许关闭或应该禁止关闭.

In WPF application together with MVVMLight Toolkit, I would like to see your opinion, what is the best way to implement if I need to Cancel the Window Close event. In Window.Closing event I can set the e.Cancel = true, which prevents closing the form. To identify if the Close is allowed, or should be prevented is in the ViewModel context.

一种解决方案是，如果我定义一个Application变量，并且可以在后面的视图代码中的常规事件处理程序中查询此变量?

One solution could be if I define an Application variable, and I can query this in the normal event handler in view code behind?

谢谢

推荐答案

使用MVVM Light，您可以获得EventToCommand:

With MVVM Light you got EventToCommand:

因此您可以在xaml中将关闭事件连接到VM.

So you could in xaml wire up the closing event to the VM.

<Window ...
        xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
        xmlns:command="http://www.galasoft.ch/mvvmlight">
<i:Interaction.Triggers>
  <i:EventTrigger EventName="Closing">
    <command:EventToCommand Command="{Binding ClosingCommand}"
                            PassEventArgsToCommand="True" />
  </i:EventTrigger>
</i:Interaction.Triggers>

并在VM中:

public RelayCommand<CancelEventArgs> ClosingCommand { get; private set; }

ctor() {
  ClosingCommand = new RelayCommand<CancelEventArgs>(args => args.Cancel = true);
}

如果您不想将CancelEventArgs传递给虚拟机:

If you do not want to pass CancelEventArgs to the VM:

您总是可以对Behavior采取类似的方法，并且只需在VM中使用简单的bool(将此布尔值绑定到行为")来指示应该取消关闭事件.

You could always take the similar approach with a Behavior and just use a simple bool from the VM(bind this bool to the Behavior) to indicate the closing event should be cancelled.

更新:

下载以下示例的链接

要使用Behavior进行此操作，您可以使用Behavior，例如:

To do this with a Behavior you could just have a Behavior such as:

internal class CancelCloseWindowBehavior : Behavior<Window> {
  public static readonly DependencyProperty CancelCloseProperty =
    DependencyProperty.Register("CancelClose", typeof(bool),
      typeof(CancelCloseWindowBehavior), new FrameworkPropertyMetadata(false));

  public bool CancelClose {
    get { return (bool) GetValue(CancelCloseProperty); }
    set { SetValue(CancelCloseProperty, value); }
  }

  protected override void OnAttached() {
    AssociatedObject.Closing += (sender, args) => args.Cancel = CancelClose;
  }
}

现在是xaml:

<i:Interaction.Behaviors>
  <local:CancelCloseWindowBehavior CancelClose="{Binding CancelClose}" />
</i:Interaction.Behaviors>

CancelClose是VM的bool属性，指示是否应取消Closing事件.在随附的示例中，我有一个Button可以从VM切换此布尔值，这应该可以让您测试Behavior

Where CancelClose is a bool property from the VM which indicates if the Closing event should be cancelled or not. In the attached example I have a Button to toggle this bool from the VM that should let you test the Behavior

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