Can not get Triggers to work

[sam-wheat]

I can not get the WinUI branch of the toolkit to build so I copied relevant XAML from this page verbatim to a sample app to try to test the functionality. I can not get the example to work. There are no error messages - the triggers do not fire. My repo with the sample app is here. I have a different but related problem to solve in my app so if I get this working I'll probably be back with another question.

Here is a copy/paste of the XAML in the page cited above:

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">

    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup >
            <VisualState x:Name="checkstate">
                <VisualState.StateTriggers>
                    <!--Checkbox is null when indeterminate-->
                    <triggers:IsEqualStateTrigger Value="{Binding IsChecked, ElementName=checkbox, Mode=OneWay}" To="{x:Null}" />
                </VisualState.StateTriggers>
                <VisualState.Setters>
                    <Setter Target="checkStatus.Text" Value="Checkbox value is indeterminate" />
                </VisualState.Setters>
            </VisualState>
        </VisualStateGroup>
        <VisualStateGroup >
            <VisualState x:Name="sliderstate">
                <VisualState.StateTriggers>
                    <triggers:IsEqualStateTrigger Value="{Binding Value, ElementName=slider, Mode=OneWay}" To="0" />
                </VisualState.StateTriggers>
                <VisualState.Setters>
                    <Setter Target="sliderStatus.Text" Value="Slider value is 0" />
                </VisualState.Setters>
            </VisualState>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>

    <StackPanel VerticalAlignment="Center" MaxWidth="400">
        <TextBlock x:Name="checkStatus" Text="Checkbox value is not indeterminate" HorizontalAlignment="Center"  />
        <CheckBox HorizontalAlignment="Left" Content="Check me" x:Name="checkbox" IsChecked="True" IsThreeState="True" />
        <Slider x:Name="slider" Minimum="0" Maximum="5" />
        <TextBlock x:Name="sliderStatus" Text="Slider value is not 0" />
    </StackPanel>

</Grid>

[niels9001]

Have you tried IsNullOrEmptyStateTrigger for the CheckBox to see if that works?

Nvm, I cloned your repro and it's a literal copy-paste :).

@michael-hawker Any known issues that this trigger doesn't work in WinUI?

[michael-hawker]

Does this code work on UWP? Like VSM is tricky to run within a page sometimes as it has to be on the root object (microsoft/microsoft-ui-xaml#5576). Though I could suspect that it could have something to do with Window not being a FrameworkElement here? That does cause issues elsewhere: microsoft/microsoft-ui-xaml#4966

Can you try putting everything in a Page and have your Window just contain that page? See microsoft/microsoft-ui-xaml#5515

I also have a new template which makes checking code against UWP and WinUI 3 a lot easier: https://github.com/michael-hawker/WinUI2plus3Template - Just include Microsoft.Toolkit.Uwp.UI in the UWP head and CommunityToolkit.WinUI.UI in the WindowsAppSDK one and follow the pattern in the template doc to abstract the namespace for the Trigger.

We should be pulling the Trigger code over in our first-wave of things when we start setting up our 8.0 code-base in the next couple of weeks, so we'll have these better tested across both platforms with examples as well.

[sam-wheat]

Can you try putting everything in a Page and have your Window just contain that page?

That was the trick! Thank you.

Now I have to make it work in a style in a control library... I might be back...