Question

I am using the MVVM model.

I have a dependency property, a boolean, called “ResultOfUpdate“. It is changed whenever a user tries to run a command.

In the setter for this dependency property I am calling “RaisePropertyChanged()” method on the property name.

It is bound to a DataTrigger like so :

<DataTrigger Binding="{Binding ResultOfUpdate}"  Value="True">
    <DataTrigger.EnterActions>
        <BeginStoryboard>
            <Storyboard>
                <DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(TextBlock.Opacity)" 
                                               AutoReverse="True">
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0"  Value="0"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.1"  Value="0.1"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.2" Value="0.2"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.3" Value="0.3"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.4" Value="0.4"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.5" Value="0.5"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.6"  Value="0.6"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.7" Value="0.7"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.8" Value="0.8"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.9" Value="0.9"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.1" Value="1"/>
                    <DiscreteDoubleKeyFrame KeyTime="0:0:0.3" Value="1"/>
                </DoubleAnimationUsingKeyFrames>
            </Storyboard>
        </BeginStoryboard>
    </DataTrigger.EnterActions>
</DataTrigger>

…

 <TextBlock Style="{StaticResource statusStyle}"  
            Opacity="0" Text="Results updated!"      
            FontSize="10" FontFamily="Segoe UI"/>

I would like for each time this bool is set to true, the storyboard is played.

Confusingly, this storyboard is then triggered correctly the first time the user runs the command, updating the dependecy property to true.

Subsequent attempts have found that the dependency property setter code is entered, and the RaisePropertyChanged() method called – but the storyboard is not played again.

What have I done incorrectly here ?

Answer 1

You could possibly use an event trigger like this:

<StackPanel>
    <TextBlock Text="I'm a text block" Name="theTextBlock"/>
    <Button Name="BeginButton">Begin</Button>
    <StackPanel.Triggers>
        <EventTrigger RoutedEvent="Button.Click" SourceName="BeginButton">
            <BeginStoryboard Name="MyBeginStoryboard">
                <Storyboard>
                    <DoubleAnimation
                        Storyboard.TargetName="theTextBlock"
                        Storyboard.TargetProperty="(TextBlock.Opacity)"
                        From="0.0" To="1.0" AutoReverse="True" Duration="0:0:1"/>
                    </Storyboard>
            </BeginStoryboard>
        </EventTrigger>
    </StackPanel.Triggers>
</StackPanel>