WPF Binding - Default value for empty string

Question

Is there a standard way to set a default or fallback value for a WPF binding if the bound string is empty?

Answer 1

I was under the impression that FallbackValue provides a value when the binding fails and TargetNullValue provides a value when the bound value is null.

To do what you want you will either need a converter (possibly with a parameter) to convert an empty string to a target value, or put the logic in your view model.

I would probably go with a converter something like this (not tested).

public class EmptyStringConverter : MarkupExtension, IValueConverter
{  
    public object Convert(object value, Type targetType, 
                          object parameter, CultureInfo culture)
    {
        return string.IsNullOrEmpty(value as string) ? parameter : value;
    }

    public object ConvertBack(object value, Type targetType, 
                              object parameter, CultureInfo culture)
    {
        throw new NotImplementedException();
    }

    public override object ProvideValue(IServiceProvider serviceProvider)
    {
        return this;
    }
}