Embedded systems directory and blog

Top 10 Must Have Features in O/R Mapping Tools

/* Note one-to-many self relationship thru "reports_to" */
CREATE TABLE t_employees (
employee_id int IDENTITY (1, 1) NOT NULL,
name nvarchar (40) NOT NULL,
birth_date datetime NULL,
photo image NULL,
reports_to int NULL,
)

// Domain object class for t_employees table
public class Employee
{
Int32			_employeeId;
String			_name;
DateTime		_birthDate;
Byte[]			_photo;
Int32			_reportsTo;
ArrayList		_subordinates;
Employee		_supervisor;

Int32 EmployeeId {
	get { return _employeeId;} set { _employeeId = value; }
}
String Name {
	get { return _name; } set { _name = value; }
}
DateTime BirthDate {
	get { return _birthDate; } set { _birthDate = value; }
}
Byte[] Photo {
	get { return _photo; } set { _photo = value; }
}
Int32 ReportsTo {
	get { return _reportsTo; } set { _reportsTo = value; }
}
ArrayList Subordinates {
	get { return _subordinates; } set { _subordinates = value; }
}
Employee Supervisor {
	get { return _employee; } set { _employee = value; }
}
}

// Persistence object for Employee class
public interface IEmployeeFactory
{
void Load(Employee object, int nDepth);
void Insert(Employee object);
void Update(Employee object);
void Delete(Employee object);

// Query methods
ArrayList FindSomeEmployees(); 

// Relationship methods
void LoadSupervisor (Employee emp);
void LoadSubordinates(Employee emp, int nDepth);
}

Below is an example of how a client application will use this code:

public class NorthwindApp
{
static void Main (string[] args) {
	Employee emp = new Employee();
	EmployeeFactory empFactory = new EmployeeFactory();

	// Let's load a employee from Northwind database.
	emp.EmployeeId = 10045;
	empFactory.load(emp);

	// empList is a collection of Employee objects
	ArrayList empList = empFactory.FindSomeEmployees();
	// subList is a collection of Employee's subordinates objects
	ArrayList subList = empFactory.LoadSubordinates(emp, 1);

	// supervisor is Employee's supervisor object
	Employee supervisor = empFactory.LoadSupervisor(emp);
}
}

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