Question

I have a WPF application with Caliburn.Micro.

I want to handle slider’s move, i.e. MouseUp event.

<Slider cal:Message.Attach="[Event MouseUp] = [Action OnSliderMouseUp($this)]"  
        Value="{Binding  PlayerPosition, Mode=OneWay}" MinWidth="200" 
        VerticalAlignment="Center" Minimum="0" 
        Maximum="{Binding Player.NaturalDuration.TimeSpan.TotalMilliseconds}"/>

In ViewModel:

public void OnSliderMouseUp(Slider slider)
{
    int blah = 9;
}

OnSliderMouseUp() is never called. Could you please tell what I am missing?

Answer 1

Actually you have two problems:

1. The Slider control does not fires the MouseUp event. If you interested in an event which fires when the user stops dragging the slider you are looking for the Thumb.DragCompleted.
   You can find more info here: WPF: Slider with an event that triggers after a user drags

2. But if you whould write

   <Slider cal:Message.Attach="[Event Thumb.DragCompleted] = [Action OnSliderMouseUp($this)]"  />
   

   it still won’t work. Because Caliburn.Micro (to be preciese System.Windows.Interactiviy.EventTrigger which is used by Calibrun.Micro) does not support attached events. For more info and a workaround see: using attached events with caliburn micro Message.Attach

So a working soultion (with the RoutedEventTrigger implementation from the above mentioned question):

<Slider Value="{Binding  PlayerPosition, Mode=OneWay}" MinWidth="200" ...>
    <i:Interaction.Triggers>                
        <local:RoutedEventTrigger RoutedEvent="Thumb.DragCompleted">
            <cal:ActionMessage MethodName="OnSliderMouseUp">
                <cal:Parameter Value="$source" />
            </cal:ActionMessage>
        </local:RoutedEventTrigger>
    </i:Interaction.Triggers>
</Slider>

Note that because Thumb.DragCompleted an attached event $this won’t work and you need to use $source instead.