.NET 6 Api multiple repositories (factory pattern)

Question

I'm quite new to .NET Core (always worked before with classic framework) and don't understand how to solve it.

I need to create an API that returns a common object from different databases. In this example, I connect to DB1 with a table called "Usuarios" and to a DB2 with a table called "Users". Both tables have different field names.

In this example I work with 2 databases, but the idea is to add more in the future. So please think on a solution with N databases.

I have 2 models, separated in folders. Each model has its own context and a User object.

As each database has a different User table property (different field names, etc), I have created a common object:

The idea is that when you use the Api for getting all users, you get IEnumerable<DTO_Usuario>

Then I have one repository for each database:

The interface defines a GetAll method:

And then, each repository implements the interface:

For context 1:

For context 2:

Now, let's look to the controller:

Looking at the controller:

I don't want to set each repository in the constructor, because when in the future I add a third database, I need to change all controllers' constructors.

I want, on each method, get a parameter to select the database to connect. In the example, the Get method has the db parameter which select the repository to use. But, of course, I don't want on each method do a switch to select the repository to use.

How is the best way to solve it?

I show also my Program.cs:

Thanks for your help

Answer 1

In the controller, you just need to add the interface like below.

public class UsuariosController : ControllerBase
    {
        private readonly IServiceProvider _serviceProvider;
        public UsuariosController(IServiceProvider serviceProvider)
        {
            _serviceProvider = serviceProvider;
        }
        [HttpGet("Get")]
        public IEnumerable<DTO_Usuario> Get(int Db)
        {
            IUsuarioRepository usuarioRepository = Db switch
            {
                1 => _serviceProvider.GetRequiredService<Usuario_DB1Repository>(),
                2 => _serviceProvider.GetRequiredService<Usuario_DB2Repository>(),
                _ => _serviceProvider.GetRequiredService<Usuario_DB1Repository>(),
            };
            return usuarioRepository.GetAll();
        }
    }

By using Microsoft.Extensions.DependencyInjection, you can call arbitrary services.

Goodluck!