DbContext interface in DDD

Question

I read that Domain project shouldn't specify any ORM. So if I have to create interface for DbContext implemented in Infrastructture project, how can I do it? How can I specify all required DbSet? Interface in Domain project:

public interface IConfigurationDbContext
{
    Task<int> SaveChangesAsync(CancellationToken cancellationToken = default);
}

Implementation in Infrastructure project:

public class ConfigurationDbContext : DbContext, IConfigurationDbContext
{
    public ConfigurationDbContext([NotNull] DbContextOptions<ConfigurationDbContext> options) : base(options)
    {
    }

    public DbSet<Client> Clients { get; set; }
    public DbSet<ApiResource> ApiResources { get; set; }
    public DbSet<ApiScope> ApiScopes { get; set; }
    public DbSet<IdentityResource> IdentityResources { get; set; }
}

As u see, IConfigurationDbContext interface doesn't contain any DbSet, because this way require to specify used ORM in Domain project. So how should I create this interface?

Answer 1

Use IQueryable to create a full-featured abstraction over your DbContext. This preserves the core query-building capabilities of the DbContext, and is easilly substituable by another type using Queryable.AsQueryable.

public interface IConfigurationRepository
{
    public IQueryable<Client> Clients { get; }
    public IQueryable<ApiResource> ApiResources { get; }
    public IQueryable<ApiScope> ApiScopes { get; }
    public IQueryable<IdentityResource> IdentityResources { get; }

    public void Add<TEntity>(TEntity e);
    public void Remove<TEntity>(TEntity e);
    public Task<int> SaveChangesAsync();
}

And you can implement this interface instead of having DbSet properties on your DbContext or you can use explicit interface implementation, eg:

    public IQueryable<Client> Clients => this.Set<Client>();

    public IQueryable<ApiResource> ApiResources => this.Set<ApiResource>();

    public IQueryable<ApiScope> ApiScopes => this.Set<ApiScope>();

    public IQueryable<IdentityResource> IdentityResources => this.Set<IdentityResource>();

If you remove the DbSet properties, you need to declare your entity types in OnModelCreating like this:

protected override void OnModelCreating(ModelBuilder builder)
{
    builder.Entity<IdentityResource>();
    builder.Entity<ApiResource>();
    builder.Entity<ApiScope>();
    builder.Entity<Client>();
    . . .

 }

And when you need the DbSet<TEntity> get it with

dbContext.Set<TEntity>()