How do I resolve the value of a databinding inside a MarkupExtension?

Question

I\'ve made a markup extension for translating strings based on a key. Example

Now I want to

Answer 1

It is not possible to get the value of a binding. You're not supposed to be even trying to do this. WPF uses some fancy reflection to resolve the bindings and trust me - you do not wan't to start trying that yourself.

Anyway with that in mind, this is what I ended up doing, which actually is a nice solution:

I made a TranslateConverter that took care of the translation:

public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
    var key = value as string ?? parameter as string;

    if (key != null)
    {
    // Do translation based on the key

    }
    return null;
}

Then in my TranslateExtension I simply do this:

var binding = Key as Binding ?? new Binding{Mode = BindingMode.OneWay};
binding.Converter = new TranslateConverter(_targetObject, _targetProperty, Dictionary, Converter);
binding.ConverterParameter = Key is Binding ? null : Key as string;

return binding.ProvideValue(serviceProvider);

This way a binding is resolved by WPF and is passed to the converter as value, while a simple text-key is passed to the converter as a paramter.

_targetObject and _targetProperty are obtained from the ServiceProvider.