Compare WPF ItemsControl item to another control's DataContext in Trigger

Question

In my C# / WPF / .NET 4.5 app I would like to implement a Trigger that toggles the Visibility of a control that resides inside the ItemTemplate for an ItemsControl.

I have another control named TheWorkspace. TheWorkspace's DataContext is set to one of the items that populate my ItemsControl. For the item that comprises TheWorkspace's DataContext, I would like to display text that indicates the item we're working on.

I need a Trigger that compares the item's DataContext to TheWorkspace's DataContext and sets the item's Visibility accordingly.

The ItemTemplate:

<DataTemplate>
  <Grid>
    <!-- ... -->
    <TextBlock Grid.Column="2"
               Text="This is the item we're working on."
               Visibility="Hidden">
      <TextBlock.Triggers>
        <!-- Pseudocode -->
        <DataTrigger Binding="{Binding TheWorkspace.DataContext}" Value="{Binding}">
        <!-- /Pseudocode -->
          <Setter Property="Visibility" Value="Visible" />
        </DataTrigger>
      </TextBlock.Triggers>
    </TextBlock>
  </Grid>
</DataTemplate>

This, unfortunately, does not work as intended.

How can I replace the pseudocode to specify a trigger that accomplishes this behavior?

Answer 1

I have solved the problem using a MultiBinding and a MultiValueConverter:

The ItemTemplate:

<DataTemplate>
  <!-- ... -->
    <TextBlock Text="This is the item we're working on.">
      <TextBlock.Style>
        <Style TargetType="TextBlock">
          <Setter Property="Visibility"
                  Value="Hidden"/>
          <Style.Triggers>
            <DataTrigger Value="True">
              <DataTrigger.Binding>
                <MultiBinding Converter="{StaticResource samenessConverter}">
                  <Binding ElementName="TheWorkspace"
                           Path="DataContext"/>
                  <Binding/>
                </MultiBinding>
              </DataTrigger.Binding>
              <Setter Property="Visibility"
                      Value="Visible"/>
            </DataTrigger>
          </Style.Triggers>
        </Style>
      </TextBlock.Style>
    </TextBlock>
  <!-- ... -->
</DataTemplate>

The MultiValueConverter:

public class SamenessConverter : IMultiValueConverter {
  public object Convert(object[] values, Type targetType, object parameter, CultureInfo culture) {
    return values.All(x => x == values[0]);
  }
  // ...
}