How do I use a boolean Value as Trigger

Raymond Osterbrink

I need a VisualStateTrigger which reacts on if a ListView.SelectedIndex > -1

My XAML looks like this:

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}"
      EntranceNavigationTransitionInfo.IsTargetElement="True">
    <VisualStateManager.VisualStateGroups>
        <VisualStateGroup>
            <VisualState x:Name="wideView">
                <VisualState.StateTriggers>
                    <AdaptiveTrigger MinWindowWidth="960"/>
                </VisualState.StateTriggers>
                <VisualState.Setters>
                    <Setter Target="ListColumn.Width" Value="420"/>
                    <Setter Target="DetailColumn.Width" Value="*"/>
                </VisualState.Setters>
            </VisualState>
            <VisualState x:Name="narrowDetailView">
                <VisualState.StateTriggers>
                    <AdaptiveTrigger MinWindowWidth="0"/>

                </VisualState.StateTriggers>
                <VisualState.Setters>
                    <Setter Target="ListColumn.Width" Value="0"/>
                    <Setter Target="DetailColumn.Width" Value="*"/>
                </VisualState.Setters>
            </VisualState>
            <VisualState x:Name="narrowListView">
                <VisualState.StateTriggers>
                    <AdaptiveTrigger MinWindowWidth="0"/>
                </VisualState.StateTriggers>
                <VisualState.Setters>
                    <Setter Target="ListColumn.Width" Value="*"/>
                    <Setter Target="DetailColumn.Width" Value="0"/>
                </VisualState.Setters>
            </VisualState>
        </VisualStateGroup>
    </VisualStateManager.VisualStateGroups>
    <Grid.ColumnDefinitions>
        <ColumnDefinition x:Name="ListColumn" Width="0"/>
        <ColumnDefinition x:Name="DetailColumn" Width="*"/>
    </Grid.ColumnDefinitions>
    <ListView x:Name="SelectionList"
              Grid.Column="0"/>
    <ListView x:Name="DetailsList"
              Grid.Column="1"/>
</Grid>

When SelectionList SelectedIndex == -1 the narrowListView-Trigger should be chosen, otherwise, the narrowDetailsView-Trigger is the desired one.

Is this possible only in XAML (and if so, what is the most efficient approach), or do I need to solve this in code-behind.

Igor Ralic

WindowsStateTriggers library is your friend.

<VisualState>
    <VisualState.StateTriggers>
        <triggers:CompareStateTrigger Value="{x:Bind someListView.SelectedIndex, Mode=OneWay}" CompareTo="-1" Comparison="GreaterThan" />
    </VisualState.StateTriggers>
<VisualState.Setters>

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