Question

I have a class in which the name of the object can be null.

public class Thing
{
    /// <summary>
    /// The identifier of the thing
    /// </summary>
    /// <remarks>
    /// This will never be null.
    /// </remarks>
    public string Identifier { get; set; }
    /// <summary>
    /// The name of the thing
    /// </summary>
    /// <remarks>
    /// This MAY be null. When it isn't, it is more descriptive than Identifier.
    /// </remarks>
    public string Name { get; set; }
}

In a Silverlight ListBox, I use a DataTemplate where I have the name bound to a TextBlock:

<DataTemplate x:Key="ThingTemplate">
    <Grid>
        <TextBlock TextWrapping="Wrap" Text="{Binding Name}" />
    </Grid>
</DataTemplate>

However, this obviously doesn’t look very good if the Name is null. Ideally, I would want to use something equivalent to

string textBlockContent = thing.Name != null ? thing.Name : thing.Identifier;

but I can’t change my model object. Is there any good way to do this?

I thought about using a Converter, but it seems to me I’d have to bind the converter to the object itself, and not the Name property. This would be fine, but how would I then rebind when either Name or Identifier changes? IValueConverter doesn’t appear to have any way to force a reconvert if I would manually listen on my object’s INotifyPropertyChanged event.

Any ideas on the best way to do this?

Answer 1

In WPF, you can do this easily by implementing an IMultiValueConverter. Unfortunately, Silverlight doesn’t support this directly, though there are workarounds written for Silverlight.