Catch Events from Within Templates

Question

Here the pretty much simplyfied code:

Code Snippet

<Page x:Name="myPageObj">

<Page.Resources>

<DataTemplate DataType="{x:Type local:ImageMenuData}">

<Border>

<Border.Triggers>

<EventTrigger SourceName="myPageObj" RoutedEvent="MyPage.NextDocEvent">

<BeginStoryboard Storyboard="{StaticResource 3dFlipAnimation}"/>

</EventTrigger>

<Border.Triggers>

</Border>

</DataTemplate>

</Page.Resources>

...

</Page>

Now I want to throw the NextDocEvent from within c# code.
The definition of the Event:

Code Snippet

public static readonly RoutedEvent NextDocEvent = EventManager.RegisterRoutedEvent( "NextDoc", RoutingStrategy.Tunnel, typeof( RoutedEventHandler ), typeof( MyPage ) );

public event RoutedEventHandler NextDoc
{

add { AddHandler( NextDocEvent, value ); }

remove { RemoveHandler( NextDocEvent, value ); }

}

void RaiseNextDocEvent()
{

RoutedEventArgs newEventArgs = new RoutedEventArgs( MyPage.NextDocEvent );
RaiseEvent(newEventArgs);

}

this approach seems not to work because I get this Error:

Code Snippet

'MyPage.NextDocEvent' value cannot be assigned to property 'RoutedEvent' of object 'System.Windows.EventTrigger'. Value cannot be null.
Parameter name: value  Error at object 'System.Windows.EventTrigger' in markup file

Answer 1

Hello, you should use RoutedEvent="local:MyPage.NextDoc", not NextDocEvent. Just like you normally use RoutedEvent="Button.Click", not ClickEvent.

 

Answer 2

stupid me! Of course.
Now it compiles but still the event is not catched.
if I call the Raise-Method the EventTrigger doesnt get the tunneled event it should shouldn't it?

Answer 3

This works fine for me:

In the Window’s code behind, create a routed event:

        public static readonly RoutedEvent TestEvent = EventManager.RegisterRoutedEvent("Test", RoutingStrategy.Tunnel, typeof(RoutedEventHandler), typeof(Window1));

 

        public event RoutedEventHandler Test

        {

            add { AddHandler(TestEvent, value); }

            remove { RemoveHandler(TestEvent, value); }

        }

 

        private void RaiseTestEvent()

        {

            RoutedEventArgs newEventArgs = new RoutedEventArgs(Window1.TestEvent);

            RaiseEvent(newEventArgs);

        }

 

Raise this event when clicking a Button (are you missing this step?):

        private void Button1_Click(object sender, RoutedEventArgs e)

        {

            RaiseTestEvent();

        }

 

Use an EventTrigger to handle this event:

                <EventTrigger RoutedEvent="local:Window1.Test">

                    <BeginStoryboard Storyboard="{StaticResource sb}"/>

                </EventTrigger>

 

The animation plays successfully.

 

 

Answer 4

Could it be that I cant catch the event because my EventTrigger is in a Template?

Answer 5

 

I have a very similar situation. My post here explains this. Have you figured out what your issue is? I have been struggling with this for a while now - need to find some alternate solutions soon if I can't figure out what is going on.

 

I have double-checked and tripple checked for syntatic/spelling errors which the compiler might not catch and have found nothing. For some reason my DataTemplate is not catching the event even though I have verified that the ListBoxItem it is applied to can from code.

 

Any suggestions out there on how to debug this?

Answer 6

DataTemplate is a NameScope (implements INameScope), so the SourceName in the EventTrigger is looking for myPageObj in the DataTemlate, not in the Page.

 

Thanks, Rob

Rob Relyea | Program Manager, WPF & Xaml Language Team
robrelyea.com | /blog | /wpf | /xaml

Answer 7

Thanks Rob that was a slightly more helpful piece of information.
So i am in another scope.
Is there a Chance to Trigger that EvenTrigger from within other scopes?
Any solution is ok even a hacky one. I need to catch that Event in the templatescope else I have to work around and remove almost all my templates and work them into my definitions.
That would be good night DRY.