Entity Framework Core Integration

This document explains how to integrate EF Core as an ORM provider to ABP based applications and how to configure it.

Installation

Volo.Abp.EntityFrameworkCore is the main nuget package for the EF Core integration. Install it to your project (for a layered application, to your data/infrastructure layer):

Install-Package Volo.Abp.EntityFrameworkCore

Then add AbpEntityFrameworkCoreModule module dependency (DependsOn attribute) to your module:

using Volo.Abp.EntityFrameworkCore;
using Volo.Abp.Modularity;

namespace MyCompany.MyProject
{
    [DependsOn(typeof(AbpEntityFrameworkCoreModule))]
    public class MyModule : AbpModule
    {
        //...
    }
}

Note: Instead, you can directly download a startup template with EF Core pre-installed.

Creating DbContext

You can create your DbContext as you normally do. It should be derived from AbpDbContext<T> as shown below:

using Microsoft.EntityFrameworkCore;
using Volo.Abp.EntityFrameworkCore;

namespace MyCompany.MyProject
{
    public class MyDbContext : AbpDbContext<MyDbContext>
    {
        //...your DbSet properties here

        public MyDbContext(DbContextOptions<MyDbContext> options)
            : base(options)
        {
        }
    }
}

Configure the Connection String Selection

If you have multiple databases in your application, you can configure the connection string name for your DbContext using the [ConnectionStringName] attribute. Example:

[ConnectionStringName("MySecondConnString")]
public class MyDbContext : AbpDbContext<MyDbContext>
{
    
}

If you don't configure, the Default connection string is used. If you configure a specific connection string name, but not define this connection string name in the application configuration then it fallbacks to the Default connection string.

Registering DbContext To Dependency Injection

Use AddAbpDbContext method in your module to register your DbContext class for dependency injection system.

using Microsoft.Extensions.DependencyInjection;
using Volo.Abp.EntityFrameworkCore;
using Volo.Abp.Modularity;

namespace MyCompany.MyProject
{
    [DependsOn(typeof(AbpEntityFrameworkCoreModule))]
    public class MyModule : AbpModule
    {
        public override void ConfigureServices(ServiceConfigurationContext context)
        {
            context.Services.AddAbpDbContext<MyDbContext>();

            //...
        }
    }
}

Add Default Repositories

ABP can automatically create default generic repositories for the entities in your DbContext. Just use AddDefaultRepositories() option on the registration:

services.AddAbpDbContext<MyDbContext>(options =>
{
    options.AddDefaultRepositories();
});

This will create a repository for each aggregate root entity (classes derived from AggregateRoot) by default. If you want to create repositories for other entities too, then set includeAllEntities to true:

services.AddAbpDbContext<MyDbContext>(options =>
{
    options.AddDefaultRepositories(includeAllEntities: true);
});

Then you can inject and use IRepository<TEntity, TPrimaryKey> in your services. Assume that you have a Book entity with Guid primary key:

public class Book : AggregateRoot<Guid>
{
    public string Name { get; set; }

    public BookType Type { get; set; }
}

(BookType is a simple enum here) And you want to create a new Book entity in a domain service:

public class BookManager : DomainService
{
    private readonly IRepository<Book, Guid> _bookRepository;

    public BookManager(IRepository<Book, Guid> bookRepository) //inject default repository
    {
        _bookRepository = bookRepository;
    }

    public async Task<Book> CreateBook(string name, BookType type)
    {
        Check.NotNullOrWhiteSpace(name, nameof(name));

        var book = new Book
        {
            Id = GuidGenerator.Create(),
            Name = name,
            Type = type
        };

        await _bookRepository.InsertAsync(book); //Use a standard repository method

        return book;
    }
}

This sample uses InsertAsync method to insert a new entity to the database.

Add Custom Repositories

Default generic repositories are powerful enough in most cases (since they implement IQueryable). However, you may need to create a custom repository to add your own repository methods.

Assume that you want to delete all books by type. It's suggested to define an interface for your custom repository:

public interface IBookRepository : IRepository<Book, Guid>
{
    Task DeleteBooksByType(BookType type);
}

You generally want to derive from the IRepository to inherit standard repository methods. However, you don't have to. Repository interfaces are defined in the domain layer of a layered application. They are implemented in the data/infrastructure layer (EntityFrameworkCore project in a startup template).

Example implementation of the IBookRepository interface:

public class BookRepository : EfCoreRepository<BookStoreDbContext, Book, Guid>, IBookRepository
{
    public BookRepository(IDbContextProvider<BookStoreDbContext> dbContextProvider)
        : base(dbContextProvider)
    {
    }

    public async Task DeleteBooksByType(BookType type)
    {
        await DbContext.Database.ExecuteSqlCommandAsync(
            $"DELETE FROM Books WHERE Type = {(int)type}"
        );
    }
}

Now, it's possible to inject the IBookRepository and use the DeleteBooksByType method when needed.

Override Default Generic Repository

Even if you create a custom repository, you can still inject the default generic repository (IRepository<Book, Guid> for this example). Default repository implementation will not use the class you have created.

If you want to replace default repository implementation with your custom repository, do it inside AddAbpDbContext options:

context.Services.AddAbpDbContext<BookStoreDbContext>(options =>
{
    options.AddDefaultRepositories();
    options.AddRepository<Book, BookRepository>(); //Replaces IRepository<Book, Guid>
});

This is especially important when you want to override a base repository method to customize it. For instance, you may want to override DeleteAsync method to delete an entity in a more efficient way:

public override async Task DeleteAsync(
    Guid id,
    bool autoSave = false,
    CancellationToken cancellationToken = default)
{
    //TODO: Custom implementation of the delete method
}

Access to the EF Core API

In most cases, you want to hide EF Core APIs behind a repository (this is the main purpose of the repository). However, if you want to access the DbContext instance over the repository, you can use GetDbContext() or GetDbSet() extension methods. Example:

public class BookService
{
    private readonly IRepository<Book, Guid> _bookRepository;

    public BookService(IRepository<Book, Guid> bookRepository)
    {
        _bookRepository = bookRepository;
    }

    public void Foo()
    {
        DbContext dbContext = _bookRepository.GetDbContext();
        DbSet<Book> books = _bookRepository.GetDbSet();
    }
}

• GetDbContext returns a DbContext reference instead of BookStoreDbContext. You can cast it, however in most cases you don't need it.

Important: You must reference to the Volo.Abp.EntityFrameworkCore package from the project you want to access to the DbContext. This breaks encapsulation, but this is what you want in that case.

Advanced Topics

Set Default Repository Classes

Default generic repositories are implemented by EfCoreRepository class by default. You can create your own implementation and use it for default repository implementation.

First, define your repository classes like that:

public class MyRepositoryBase<TEntity>
    : EfCoreRepository<BookStoreDbContext, TEntity>
      where TEntity : class, IEntity
{
    public MyRepositoryBase(IDbContextProvider<BookStoreDbContext> dbContextProvider) 
        : base(dbContextProvider)
    {
    }
}

public class MyRepositoryBase<TEntity, TKey>
    : EfCoreRepository<BookStoreDbContext, TEntity, TKey>
    where TEntity : class, IEntity<TKey>
{
    public MyRepositoryBase(IDbContextProvider<BookStoreDbContext> dbContextProvider)
        : base(dbContextProvider)
    {
    }
}

First one is for entities with composite keys, second one is for entities with single primary key.

It's suggested to inherit from the EfCoreRepository class and override methods if needed. Otherwise, you will have to implement all standard repository methods manually.

Now, you can use SetDefaultRepositoryClasses option:

context.Services.AddAbpDbContext<BookStoreDbContext>(options =>
{
    options.SetDefaultRepositoryClasses(
        typeof(MyRepositoryBase<,>),
        typeof(MyRepositoryBase<>)
    );
    //...
});

Set Base DbContext Class or Interface for Default Repositories

If your DbContext inherits from another DbContext or implements an interface, you can use that base class or interface as DbContext for default repositories. Example:

public interface IBookStoreDbContext : IEfCoreDbContext
{
    DbSet<Book> Books { get; }
}

IBookStoreDbContext is implemented by the BookStoreDbContext class. Then you can use generic overload of the AddDefaultRepositories:

context.Services.AddAbpDbContext<BookStoreDbContext>(options =>
{
    options.AddDefaultRepositories<IBookStoreDbContext>();
    //...
});

Now, your custom BookRepository can also use the IBookStoreDbContext interface:

public class BookRepository : EfCoreRepository<IBookStoreDbContext, Book, Guid>, IBookRepository
{
    //...
}

One advantage of using interface for a DbContext is then it becomes replaceable by another implementation.

Replace Other DbContextes

Once you properly define and use an interface for DbContext, then any other implementation can replace it using the ReplaceDbContext option:

context.Services.AddAbpDbContext<OtherDbContext>(options =>
{
    //...
    options.ReplaceDbContext<IBookStoreDbContext>();
});

In this example, OtherDbContext implements IBookStoreDbContext. This feature allows you to have multiple DbContext (one per module) on development, but single DbContext (implements all interfaces of all DbContexts) on runtime.