Factory methods, Private abstract/interface methods.

Wedon't have to call "UpDateDerived" explicietely as it is being called from the Update() method of the base Employee class automatically. The client program just calls "Update" on the HourlyEmployee and every thing will be taken care automatically.

Here is how things will work:

in the client code (may be a Main method) it may be like this:

Employee emp = new HourlyEmployee();

emp.Update();

The "Update" method is only defined in the "Employee" base class only.  If the Update is called on the derived class object of "Employee", in our example "HourlyEmployee" then base "Employee" class's "Update" is called. Not only that as the base class's "Update" method calls into "UpdateDerived" method which is just declared (abstract with no code) in the base class but actuall code is there in the derived class, the derived class gets the oppertunity to do its own extra Updates() in its "UpdateDerived" method that it implements. So it is like whne "Update" method on the derived class object is called, then base classes's Update is called it finishes it job and hands control over to the derived class to do the extra stuff.

I hope I explained well

I think you need to use "template" method pattern. I don't know VB, so I am giving it in C# but concept should be the same

Base Class:

public abstract class Employee

{

   public void Update()

   {

      Log("Updating employee");

      WriteToDatabase();

      // Do updations Now:

      Update1();

      Update2();

      // Following is the Template Method Call. We could call this either before

      // updations (above ones) or here i.e. after the base class updation is done

      // It depends on the requirement

      UpdateDerived(); // Hook (Template Method) into the Derived class

   }

   // This template method is made "abstract", so that the derived classes "must"

   // implement it if they don't want to be abstract. However a default "body with no code"

   // could also be given. In that case this "Employee" class is nolonger abstract

   protected abstract void UpdateDerived();

}

public class HourlyEmployee(): Employee

{

   protected override void UpdateDerived()

   {

      // Do your derived class updations here

   }

}