Keep your Entity Framework entities clean with EntityTypeConfiguration

01 Dec 2015 entity-framework, entity-type-configuration, mapping

What?

Entity Framework has two ways of mapping an entity class to a database table
- Attributes
  - Pollutes the classes
  - Avoid using this approach
- EntityTypeConfiguration
  - Unobtrusive way of mapping
  - Always use this approach

How?

Steps
- Create a mapping class for every entity
  - Inherit from the EntityTypeConfiguration class
  - Configure mapping in the constructor
- Add all the mapping classes to the DbContext

Entity

public class Employee
{
    public int Id{ get; set; }
    public string FirstName{ get; set; }
    public string LastName{ get; set; }
    public string Email{ get; set; }
}

Mapping Class

public class EmployeeMap : EntityTypeConfiguration<Employee>
{
    public EmployeeMap()
    {
        ToTable("Employees");

        HasKey(x => x.Id);

        Property(x => x.Id).HasColumnName("Id");
        Property(x => x.FirstName).HasColumnName("FirstName");
        Property(x => x.LastName).HasColumnName("LastName");
        Property(x => x.Email).HasColumnName("Email");
    }
}

DbContext

public class MyDbContext : DbContext
{
    public MyDbContext() : base("ConnectionStringKey")
    {
    }

    protected override void OnModelCreating(DbModelBuilder builder)
    {
        builder
            .Configurations
            .AddFromAssembly(typeof (MyDbContext).Assembly);
        
        base.OnModelCreating(builder);
    }
}