How can I display a different ToolTip based on the DataContext DataType in Wpf?

Question

I have an abstract UserControl that I want to show a ToolTip on. This ToolTip should be different based on the Type of the DataContext which is defined in the derived UserControls.

Is there a way to define a different ToolTip for each type in the base class? If not, how can I set this ToolTip in the derived UserControl?

Here is how I thought I would go:

<UserControl ...
  <UserControl.ToolTip>
    <DataTemplate DataType="{x:Type Library:Event}">
      <StackPanel>
        <TextBlock FontWeight="Bold" Text="{Binding Name}" />
        <TextBlock>
          <TextBlock.Text>
            <Binding Path="Kp" StringFormat="{}Kp: {0}m" />
          </TextBlock.Text>
        </TextBlock>
      </StackPanel>
    </DataTemplate>
  </UserControl.ToolTip>
</UserControl>

Answer 1

Couldn't you author a custom ValueConverter that returns the information you'd like to display for the type?

You could 'fancy this up' a bit to allow the converter to accept data templates like you're suggesting, but this will totally enable your scenario.

First, create the value converter. Pardon my quick code:

public class ToolTipConverter : IValueConverter
{
     public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    UIElement tip = null;

    if (value != null)
    {
        // Value is the data context
        Type t = value.GetType();
        string fancyName = "Unknown (" + t.ToString() + ")";

        // Can use IsInstanceOf, strings, you name it to do this part...
        if (t.ToString().Contains("Person"))
        {
            fancyName = "My custom person type";
        };


        // Could create any visual tree here for the tooltip child
        TextBlock tb = new TextBlock
        {
            Text = fancyName
        };
        tip = tb;
    }

    return tip;
}

public object ConvertBack(object o, Type t, object o2, CultureInfo ci)
{
    return null;
}

}

Then instantiate it in your user control's resources (I defined the xmlns "local" to be this namespace and assembly):

    <UserControl.Resources>
    <local:ToolTipConverter x:Key="toolTipConverter" />
</UserControl.Resources>

And make sure the root visual of your user control binds its ToolTip property:

<Grid 
    ToolTip="{Binding Converter={StaticResource toolTipConverter}}"
    Background="Blue">
    <!-- stuff goes here -->
</Grid>