Binding converter as inner class?

I was thinking about this problem again, and I came up with something similar to Dennis's solution : create a "proxy" converter class, with a Type property, which will create the instance of the actual converter and delegate the conversion to it.

public class Converter : IValueConverter
{
    private Type _type = null;
    public Type Type
    {
        get { return _type; }
        set
        {
            if (value != _type)
            {
                if (value.GetInterface("IValueConverter") != null)
                {
                    _type = value;
                    _converter = null;
                }
                else
                {
                    throw new ArgumentException(
                        string.Format("Type {0} doesn't implement IValueConverter", value.FullName),
                        "value");
                }
            }
        }
    }

    private IValueConverter _converter = null;
    private void CreateConverter()
    {
        if (_converter == null)
        {
            if (_type != null)
            {
                _converter = Activator.CreateInstance(_type) as IValueConverter;
            }
            else
            {
                throw new InvalidOperationException("Converter type is not defined");
            }
        }
    }

    #region IValueConverter Members

    public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        CreateConverter();
        return _converter.Convert(value, targetType, parameter, culture);
    }

    public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
    {
        CreateConverter();
        return _converter.ConvertBack(value, targetType, parameter, culture);
    }

    #endregion
}

You use it like that :

<Window.Resources>
    <my:Converter x:Key="CornerRadiusConverter" Type="{x:Ty