Entity Splitting in Entity Framework

I have done a lot of post on Entity Framework Code First which includes some simple tips and tricks to more complex scenarios of mapping relationship and here are some of those post if you want to read them.

Entity Framework Tutorial

However recently I was helping a friend of mine to understand Entity Framework modelling for a legacy system. Since the schema is already defined it becomes a bit difficult to create a rich domain model keeping the model in your design. The other thing I have seen is that people simply follow the schema and let schema dictating what your domain is, which in my opinion is not correct.

Anyways, after some discussion I realized that they are not taking advantage of Entity Splitting in Entity Framework, so I thought about blogging it.

Entity Splitting:- In this scenario there is a single entity or domain object but the data is stored in multiple tables with a one to one relationship. For example lets say the domain is a fitness/health industry and you have customer table which stores basic information like first name, last name, DOB in the customer table and other vital stats like resting heat beat,blood type,cholesterol level, blood pressure, Sugar level etc. in their health information table. However in your domain model the customer object is composed of both information.

Lets see this in action.

Customer.cs

public class Customer
{
    public int Id { get; set; }

    public string FirstName { get; set; }

    public string LastName { get; set; }

    public DateTime DOB { get; set; }

    public int RestingHeartBeat { get; set; }

    public string BloodType { get; set; }

    public decimal Cholesterol { get; set; }

    public string BloodPressure { get; set; }
}

So this is my domain object which represents the whole customer object however in the legacy system some information is stored in the Customer table and some in the VitalStats table.

And lets write the configuration for customer in which we will split the entity into two different tables using the Map and ToTable function as shown below.

CustomerConfiguration.cs

public class CustomerConfiguration : EntityTypeConfiguration<Customer>
{
    public CustomerConfiguration()
    {
        this.Map(c =>
       {
           c.Properties(p => new
           {
               p.Id,
               p.FirstName,
               p.LastName,
               p.DOB
           });
           c.ToTable("Customer");
       })
        .Map(v =>
       {
           v.Properties(p => new
           {
               p.Id,
               p.BloodPressure,
               p.BloodType,
               p.Cholesterol,
               p.RestingHeartBeat
           });
           v.ToTable("VitalStats");
       });
    }
}

And here is my DbContext class.

public class HealthContext : DbContext
{
    DbSet<Customer> Customer { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Conventions.Remove<PluralizingTableNameConvention>();
    }
}