How to trigger DataTemplateSelector when property changes?

问题

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 :(

回答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>

回答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.

回答3:

Just as an extra choice - if you want to stick to your templates, just use s binding with converter.

来源：https://stackoverflow.com/questions/8715315/how-to-trigger-datatemplateselector-when-property-changes

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datatemplateselector