Well, you certainly CAN inherit from your context, but the real question is why would you?
Inheritance is a concept that is used to create an "is a" relationship. In other words, your QTDAL "is a" BaseEntities. So you can treat a QTDAL as a BaseEntities object. You do not appear to be using it that way. Instead, you seem to be wanting to wrap the BaseEntities functionality.
In which case, you should simply be using BaseEntities as a member of your QTDAL class.