/// <summary>
/// The subsequent Bind* operations only apply when the Attribute's property is null.
/// </summary>
/// <param name="propertyName"></param>
/// <returns></returns>
public FluentBindingRule <TAttribute> WhenIsNull(string propertyName)
{
var prop = ResolveProperty(propertyName);
AppendFilter(FilterNode.Null(prop));
return(this);
}
