DataTrigger在ListBox.ItemTemplate中不起作用

Question

Let me give a brief overview of my issue.

I have a Window that has a ViewModel as a data context. This window also has 2 User Controls within it. These user controls have various xaml objects that bind to properties in the ViewModel, and I am having no problems with any other properties.

The issue I am having is that a data trigger that I have created will not fire. Below you can see the xaml for the data trigger that I have tried:

Note: IsBold is a property within the ViewModel that I am using for the Window. I am under the impression that user controls within a window will inherit the data context from the parent, so I don't think that is my problem.

<ScrollViewer >
        <ListBox
            ItemsSource="{Binding Path=Listings}"
            SelectionMode="Single"
            SelectedValue="{Binding Path=SelectedListingItemID}"
            SelectedValuePath="ItemID"
            Grid.IsSharedSizeScope="True">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <Grid>
                        <TextBlock>
                            <TextBlock.Style>
                                <Style TargetType="TextBlock">
                                    <Setter Property="Text" Value="NotTriggered" />
                                    <Style.Triggers>
                                        <DataTrigger Binding="{Binding Path=IsBold}" Value="True">
                                            <Setter Property="Text" Value="Triggered" />
                                        </DataTrigger>
                                    </Style.Triggers>
                                </Style>
                            </TextBlock.Style>
                        </TextBlock>
                    </Grid>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </ScrollViewer>

When I run this, I will get the output statement:

BindingExpression path error: 'DataContext' property not found on 'object' ''DataRowView'

This message leads me to believe that I need to move the data trigger to another part of the xaml so that it realizes that the property is from the ViewModel and not the ListBoxItem, but where do I move it? Or is that even the right thing to do?

I hope I was clear enough in all the necessary areas, but if I wasn't, I can certainly elaborate where needed.

Thanks for your help!

Answer 1

The easiest thing to do is to use relative source property , you can check IsBold from your window's dataContext using FindAncestor mode and AncestorType of Window, something like this:

<DataTrigger Binding="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}, Path=IsBold}" Value="True">
    <Setter Property="Text" Value="Triggered" />
</DataTrigger>