Bounded Contexts and EF Code First - How to put them together?

Question

IMHO, one of the most brilliant DDD concept is the ability of separate contexts in a application. But I'm confused on how I can put everything to work together.

First, I know that one thing is not related to other. But my question falls exactly on the Infrastructure/ORM part.

For example, I have a domain object called Procedure (a medical procedure). In the Context of Registration, only thing that matters is Code and Name. But in Procedure Management Context, I have a lot of other fields like Price that belongs to this context specific.

How I can have two entities with same name (in different contexts) with different properties using EF Code First? Basically, I want to save all fields in the same table, but retrieve only 2 fields in one context, and all fields in other. How I can achieve this?

Answer 1

The following is inspired by the Shrink EF Models with DDD Bounded Contexts article.

Domain models:

namespace SO25454395.Domain.Registration
{
    using System;

    public class Procedure
    {
        public int Id { get; set; }
        public Guid Code { get; set; }
        public string Name { get; set; }
    }
}

.

namespace SO25454395.Domain.ProcedureManagement
{
    using System;

    public class Procedure
    {
        public int Id { get; set; }
        public Guid Code { get; set; }
        public string Name { get; set; }
        public decimal Price { get; set; }
    }
}

Bounded contexts:

namespace SO25454395.Infrastructure
{
    using System.Data.Entity;

    public class RegistrationContext : BaseContext<RegistrationContext>
    {
        public DbSet<Domain.Registration.Procedure> Prodedures { get; set; }
    }
}

.

namespace SO25454395.Infrastructure
{
    using System.Data.Entity;

    public class ProcedureManagementContext : BaseContext<ProcedureManagementContext>
    {
        public DbSet<Domain.ProcedureManagement.Procedure> Procedures { get; set; }
    }
}

The default Code First behavior is to create a new database for each context, so we disable this using a base class and specify the database that should be shared among all contexts.

namespace SO25454395.Infrastructure
{
    using System.Data.Entity;

    public class BaseContext<TContext> : DbContext where TContext : DbContext
    {
        static BaseContext()
        {
            Database.SetInitializer<TContext>(null);
        }

        protected BaseContext() : base("Database")
        {

        }
    }
}

Finally we need a context containing all classes used to build the complete model. This context is used for initialization.

namespace SO25454395.Infrastructure
{
    using SO25454395.Domain.ProcedureManagement;
    using System.Data.Entity;

    public class DatabaseContext : DbContext
    {
        public DbSet<Procedure> Procedures { get; set; }

        public DatabaseContext() : base("Database")
        {
        }
    }
}

Test:

namespace SO25454395.Tests
{
    using SO25454395.Infrastructure;
    using System;
    using System.Linq;
    using Xunit;

    public class BoundedContextTests
    {
        [Fact]
        public void Test()
        {
            using (var databaseContext = new DatabaseContext())
            {
                databaseContext.Database.Initialize(true);
            }

            var code = Guid.NewGuid();
            var name = "Name";
            var price = 123.45m;

            using (var procedureManagementContext = new ProcedureManagementContext())
            {
                var procedure = new Domain.ProcedureManagement.Procedure { Code = code, Name = name, Price = price };
                procedureManagementContext.Procedures.Add(procedure);
                procedureManagementContext.SaveChanges();
            }

            using (var registrationContext = new RegistrationContext())
            {
                var procedure = registrationContext.Prodedures.Single(p => p.Code == code);
                Assert.Equal(name, procedure.Name);
                // procedure.Price is not available here.
            }
        }
    }
}