using System;
using System.Data.Entity;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            using (MyContext context = new MyContext())
            {
                bool b = context.Database.CreateIfNotExists();

                MyClassToA toA = new MyClassToA() { A = "A" };
                context.MyClasses.Add(toA);

                MyClassToB toB = new MyClassToB() { B = "B" };
                context.MyClasses.Add(toB);

                context.SaveChanges();
            }
        }
    }

    public abstract class MyClass
    {
        public MyClass()
        {
            this.Id = Guid.NewGuid();
        }

        public Guid Id { get; private set; }

        public string Name { get; set; }
    }

    public class MyClassToA : MyClass
    {
        public string A { get; set; }
    }

    public class MyClassToB : MyClass
    {
        public string B { get; set; }
    }

    public sealed class MyContext : DbContext
    {
        public DbSet<MyClass> MyClasses { get; set; }

        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);

            modelBuilder.Entity<MyClass>().Map<MyClassToA>(m => m.Requires("Discriminator").HasValue("A").IsRequired());
            modelBuilder.Entity<MyClass>().Map<MyClassToB>(m => m.Requires("Discriminator").HasValue("B").IsRequired());
        }
    }
}