Is it possible to handle the Storyboard.Completed Event in such a way that a command from the ViewMo-CodePudding

I solved the problem in such a way that there is an EventHandler in the Code-Behind which then calls the corresponding Command of the ViewModel.

<Storyboard x:Key="StartNewGameAnimation" RepeatBehavior="1x"
            Completed="StartAnimationCompleted">

private void StartAnimationCompleted(object sender, EventArgs e)
{
    var gameBoardViewModel = (GameBoardViewModel)this.DataContext;
    gameBoardViewModel.StartGameWhenStartanimationCompletedCommand.Execute(null);
}

This solution works fine, but I want to handle the Event directly in Xaml and also call the Command. It is simply important to me whether this path exists.

CodePudding user response：

You can use the Microsoft.Xaml.Behaviors.Wpf NuGet package that replaces the legacy Interactivity types. There is an InvokeCommandAction type that can invoke a command through an EventTrigger.

However, the direct way inside Storyboard does not work.

<Storyboard x:Key="StartNewGameAnimation" RepeatBehavior="1x">
   <b:Interaction.Triggers>
      <b:EventTrigger EventName="Completed">
         <b:InvokeCommandAction Command="{Binding StartGameWhenStartanimationCompletedCommand}"/>
      </b:EventTrigger>
   </b:Interaction.Triggers>
</Storyboard>

It will throw an exception at runtime, because the Storyboard cannot be frozen with the binding.

'Microsoft.Xaml.Behaviors.Interactivity.EventTrigger' must have IsFrozen set to false to modify

A workaround is to move the interaction block to a parent element, e.g. BeginStoryboard and refer to the Storyboard with an ElementName binding.

<BeginStoryboard>
   <b:Interaction.Triggers>
      <b:EventTrigger EventName="Completed" SourceObject="{Binding ElementName=StartNewGameAnimation}">
         <b:InvokeCommandAction Command="{Binding StartGameWhenStartanimationCompletedCommand}"/>
      </b:EventTrigger>
   </b:Interaction.Triggers>
   <!-- ...other code. -->
   </Storyboard>
</BeginStoryboard>

Depending on the context, setting the SourceName instead of SourceObject works, too.

<b:EventTrigger EventName="Completed" SourceName="StartNewGameAnimation">

By the way, you have to add the following XML namespace in your control, to refer to the types:

xmlns:b="http://schemas.microsoft.com/xaml/behaviors"