After reading the book I decided to use the BLL/DAL architecture in my current project. So far I've gotten the layers written in a similar way to the book (3 files per object: business obj, data obj, and obj provider), but I've run into something that the book doesn't address and I'm having trouble finding info on.

All of the objects in the book are made up of simple typed properties (DateTime, int, string, etc).

In my application (for a school) I've got an object "Student" that among other things contains 3 "Contact" objects. One has the contact info (address,phone,email,etc) for the student, and then a Contact for each parent.

My problem is that I don't know where to put the code in the Student files than manages the Contact objects.

For example if I do:
Student joe = Students.GetStudentByID(15);
joe.Grade = "A";
joe.ContactInfo.phone = "555-5555";
joe.Father.email = "[email protected]";
joe.Update();

Should the Student object update the Contact object in the business layer or in the data layer?

All object updates like this are handled in the business layer first. Then, you have to decide how to persist the OOP class changes in the underlying DB.

Typically the DAL won't have much business object support, but will only be a light layer around SQL and stored procs. The interface between the DAL and the BLL should be simpler and lower-level than the interface between the BLL and UI code.

That's doesn't mean you can't use objects at all between DAL and BLL. But the common usage is to use data container classes, or DataSets, or DataReaders there. An .Update method is OK, but not something more advanced that would involve data manipulation and not merely persistance.

The gray area is always filtering. I prefer to filter using SQL, so this blurs my boundaries :-(

Eric

So if I understand right in my example you'd have code like this in the Student BLL class:

class Student : BizObject {

method void Update() {

    this.ContactInfo.Update();
    this.Father.Update();

    this.Update(this.StudentID, this.Grade, this.ContactID, this.FatherID, etc)

}
...}

That would be fine. Then the DAL determines what to do in order to implement the Update method.

Eric