EF6 Code First and mapping via annotations, how do I build the configuration?

Question

I was using EF6's fluent mapping like this:

public SomeClass
{
    public int SomeID { get; set; }
}

public SomeClassMap : EntityTypeConfiguration<SomeClass>
{
    public SomeClassMap()
    {
        ToTable("SomeTable");
        HasKey(c => c.SomeID);
    }
}

And building the configuration from the assembly of the first requested type (model):

public class MyContext : DbContext
{
    private Assembly _assembly;

    public MyContext(string connectionName, Type type)
    {
        //checks
        Database.Connection.ConnectionString = ConfigurationManager.ConnectionStrings[connectionName].ConnectionString;

        _assembly = Assembly.GetAssembly(type);
    }

    public override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        //conventions

        //Not the ideal solution, still looking for something better
        modelBuilder.Configurations.AddFromAssembly(_assembly);
    }
}

Now I want to make a generic Data project, independent of the models, so I'd like to map via annotations and simply call the generic methods in my Data project.

I've mapped the class:

[Table("SomeTable")]
public SomeClass
{
    [Key]
    public int SomeID { get; set; }
}

Now how do I pass this to the Data project so it can build the model configuration?

Edit This might be relevant, since my Data project is generic, I don't have the DbSet<Entity> variables in it, instead I'm calling the context.Set<Entity> and using the functions from there.

Gert Arnold · Accepted Answer · 2015-03-29 00:12:19Z

You can create a DbContext by the constructor that takes a DbCompiledModel.

You can build the compiled model separately. It's up to you where you want to implement that responsibility, but the model classes should be in scope.

Here's an example:

Some classes:

[Table("Company")]
class Company
{
    [Key]
    public int CompanyID { get; set; }
    public string Name { get; set; }

    public virtual ICollection<Location> Locations { get; set; }
}

[Table("Location")]
class Location
{
    [Key]
    public int LocationID { get; set; }
    public string Name { get; set; }

    [ForeignKey("Company")]
    public int CompanyID { get; set; }
    public virtual Company Company { get; set; }
}

And the creation + usage of a DbContext:

// Create a model + register types to it.
var mb = new DbModelBuilder();
mb.Entity<Company>();
mb.Entity<Location>();

// Or:
//mb.RegisterEntityType(typeof(Company));
//mb.RegisterEntityType(typeof(Location));

// Build and compile the model
var connString = @"server=myServer;database=theDataBase;Integrated Security=SSPI;MultipleActiveResultSets=True";

var dbModel = mb.Build(new SqlConnection(connString));

var compiledModel = dbModel.Compile();

// Create a DbContext using the compiled model.
var db = new DbContext(connString, compiledModel);
Database.SetInitializer<DbContext>(null); // Prevent creation of migration table

// Ready to go!
var companies = db.Set<Company>().Include(c => c.Locations).ToList();

You can make this more efficient by storing and reusing cached DbCompiledModels.

Worked perfectly, and thank you for the suggestion of caching models!

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