Question

I have a ContentControl that I need to set it’s ContentTemplate dynamically.

so I decided to write 2 DataTemplates, and then style my ContentControl such that a trigger fires and set the proper template (dt1/dt2) when a Boolean dependency property in my view-model changes (true/false).

But the problem is if the Boolean property is primarily set to true, the data template will always be dt1 and changing the property to false wont change the template to dt2.

since the data triggers are bound to the Boolean dependency property, shouldn’t changing the property result in firing the triggers?

notes:

• There is a button in MyView which changes BooleanDependencyProp on it’s
  click event.
• MyViewModel inherits from an interface that
  implements INotifyPropertyChanged.

Xaml:

<UserControl x:Class="Views.MyView">
...

<StackPanel>
    <ContentControl Content="{Binding RelativeSource={RelativeSource AncestorType=MyView}, Path=MyViewModel}">
        <ContentControl.Style>
            <Style TargetType="{x:Type ContentControl}">
                <Style.Triggers>
                    <DataTrigger Binding="{Binding BooleanDependencyProp}" Value="true">
                                                <Setter Property="ContentTemplate">
                                                    <Setter.Value>
                                                        <dt1 ... />
                                                    </Setter.Value>
                                                </Setter>
                    <DataTrigger Binding="{Binding BooleanDependencyProp}" Value="false">
                                                <Setter Property="ContentTemplate">
                                                    <Setter.Value>
                                                        <dt2 ... />
                                                    </Setter.Value>
                                                </Setter>
                    </DataTrigger>
                </Style.Triggers>
            </Style>
        </ContentControl.Style>
    </ContentControl>
</StackPanel>

Answer 1

This is a known shortcoming of the WPF framework, if you want to apply different data templates, consider either using the visual state manager to change the presentation, or swap out the content data template for a user control that changes based on the triggers instead, you’ll get more mileage.

There’s a lot more I could say, but it would involve knowing your scenario and the differences in these DataTemplates, why you are disambiguating, etc. Also, MVVM all around? or straight ahead Code+Markup style with a few view models?