How to specify composition in model-first EF?

Question

I have following Domain.

Role is an abstract class. Programmer extends Role. Employee has multiple Roles like Programmer, Manager, etc.

I want to create a Model for it. How can we specify this composition of Roles in Employees entity?

Note: I cannot add EmpID in Roles table. Because same Role will be applicable for many employees.

Current Model

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Pseudo Code for Required Conceptual model

public abstract class Role
{
    public abstract string RoleName { get; }
    public abstract int RoleID { get; }
}

public class ProgrammerRole : Role
{
    public override string RoleName { get { return "Programmer"; } }
    public override int RoleID { get { return 101; } }
}

public class ManagerRole : Role
{
    public override string RoleName { get { return "Manager"; } }
    public override int RoleID { get { return 102; } }
}


public class Employee
{
    private IList<Role> roles;
    public IList<Role> RolesList
    {
        get
        {
            return roles;
        }
    }


    public int EmployeeID { get; set; }

    //Constructor
    public Employee()
    {
        roles = new List<Role>();
    }

    public void TerminateEmployeeByRole(Role role)
    {
        if (RolesList == null)
        {
            //If employee has no role, make as inactive
            isActiveEmployee = false;
        }
        else
        {
            //If employee has no role other than the input role, make as inactive
            RolesList.Remove(role);
            if (RolesList.Count == 0)
           {
                isActiveEmployee = false;
            }
        }
    }

}

Generally speaking, each model class generally represents a collection object like `table`, so `class Employee` represents `Employee` table. Similarly, `ProgrammerRole` and `ManagerRole` would create two tables in the database. I am sure this is not what you want. — Vivek Jain, Jun 20 '13 at 07:06

score 0 · Answer 1 · answered Jun 20 '13 at 07:22

This can be implemented in a simpler way:

public class Role
{
    public string RoleName { get; }
    public int RoleID { get; }
}

public class Employee
{
    public IList<int> RoleID { get; set; } // to store role id. This would form a table column
    [ForeignKey("RoleID")]
    public virtual IList<Role> RolesList { get; set; } // to reference Roles in the code. This will not for a table column

    public int EmployeeID { get; set; }

    //Constructor
    public Employee()
    {
        roles = new List<Role>();
    }

    public void TerminateEmployeeByRole(Role role)
    {
        if (RolesList == null)
        {
            //If employee has no role, make as inactive
            isActiveEmployee = false;
        }
        else
        {
            //If employee has no role other than the input role, make as inactive
            RolesList.Remove(role);
            if (RolesList.Count == 0)
            {
                isActiveEmployee = false;
            }
        }
    }
}

The reason for this design is that you would not be able to create more classes if more roles are added. You may create a wrapper class to fetch role details from the database.

Please use this as a starting point and not as a copy-paste solution.

How to specify composition in model-first EF?

1 Answers1