How to trigger DataTemplateSelector when property changes?

Question

I have ContentPresenter with DataTemplateSelector:

    ...      public override DataTemplate SelectTemplate(object item, DependencyObject container)     {         var model = item as ItemControlViewModel;          if (model.CurrentStatus == PrerequisitesStatus.Required)         {             return RequiredTemplate;         }          if (model.CurrentStatus == PrerequisitesStatus.Completed)         {             return FinishedTemplate;         }          ...          return InProgressTemplate;     } 

When CurrentStatus is changed, OnPropertyChanged is called.

I need somehow to trigger this DataTemplateSelector when the property is changed and change ContentPresenter DataTemplate. Any suggestions?

Threre are similar questions: 1 2, but I don't want to use any DataTriggers, because of too much states.

Tried to play with DataTriggers

    <ContentPresenter         Grid.Column="1"         Height="16"         Width="16"         Margin="3">         <ContentPresenter.Triggers>             <DataTrigger Binding="{Binding Path=CurrentStatus}" Value="0">                 <Setter Property="ContentPresenter.ContentTemplate" Value="{StaticResource ResourceKey=_requiredStatusTemplate}" />             </DataTrigger>         </ContentPresenter.Triggers>     </ContentPresenter> 

But got an error: Triggers collection members must be of type EventTrigger :(

Answer 1

As you requested an example with datatriggers in the comments, here you are:

A FrameworkElement can only have EventTriggers, therefore you get the error Message Triggers collection members must be of type EventTrigger

And also don't use a ContentPresenter directly, it is meant to be used inside a ControlTemplate. Better use a ContentControl when you want to have dynamic content. See What's the difference between ContentControl and ContentPresenter?

And finally here's a suggestion to your DataTrigger issue. I have put it inside a style for reusability ....

XAML :

<Window x:Class="WpfApplication88.MainWindow"         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"         Title="MainWindow" Height="350" Width="525">   <Window.Resources>      <DataTemplate x:Key="requiredTemplate">       <TextBlock Text="requiredTemplate"></TextBlock>       <!--your stuff here-->     </DataTemplate>      <DataTemplate x:Key="completedTemplate">       <TextBlock Text="CompletedTemplate"></TextBlock>       <!--your stuff here-->     </DataTemplate>      <Style x:Key="selectableContentStyle" TargetType="{x:Type ContentControl}">       <Style.Triggers>         <DataTrigger Binding="{Binding Path=CurrentStatus}" Value="Required">           <Setter Property="ContentTemplate" Value="{StaticResource requiredTemplate}" />         </DataTrigger>         <DataTrigger Binding="{Binding Path=CurrentStatus}" Value="Completed">           <Setter Property="ContentTemplate" Value="{StaticResource completedTemplate}" />         </DataTrigger>         <!--  your other Status' here -->       </Style.Triggers>     </Style>    </Window.Resources>    <Grid>     <ContentControl Width="100" Height="100" Style="{StaticResource selectableContentStyle}"/>   </Grid>  </Window> 

Answer 2

I could be wrong, but I believe the DataTemplateSelector is only used when the ItemContainerGenerator creates a container for an item added to the collection. Because a new container isn't generated when a property value changes, a new DataTemplate is never going to be applied via the selector.

As suggested in the comments, I would recommend you look at the VisualStateManager or data triggers, otherwise you're going to have to recreate the container for every item when one or more properties change value.