Two-level concepts

Question

I find myself lately implementing the same concept twice, once at a low level and once at a higher level. Let me see if I can explain it...

For example, given the notion of a database, I have one interface (say IDatabase) with methods like

void AddCompany(Company company);

which is what I consider "low level".

However, there are cases where I need to group a few of these calls (say I'm adding both a company and a user). I don't want to pollute the low level interface / implementation with this method, especially since this method basically only groups a few IDatabase calls, so I create a new interface. My problem is: what do I call this new interface? IHighLevelDataAccess just sounds weird.

I have the same problem with, say, remote access. One interface / implementation for the raw calls (one method maps to one web call) and another one for more complex logic (but mostly still doing remote calls).

Is there a naming convention that is expected / recommended in such cases? A design pattern that eludes me?

Answer 1

As @Ewan mentioned his comment, you need Repository Layer and Service Layer.

I also prefer adding Facade Layer in Service Layer. By this way, you can begin a transaction and can call kind of methods even they are not related.

For example, you have UserService and CompanyService. Normally, there is not required to create User and Company same time but you want to do that. So, create a facade CompanyFacade, which acts like other services but there is no or less business code, add a method CreateCompanyByAddingUser and begin transaction there.

public class CompanyFacade
{
    private readonly ICompanyService _companyService;
    private readonly IUserService _userService;
    private readonly Context _context;

    public CompanyFacade(Context context, ICompanyService companyService, IUserService userService)
    {
        _context = context;
        _companyService = companyService;
        _userService = userService;
    }


    public void CreateCompanyByAddingUser(CompanyAndUserDTO dto)
    {
        using (_context.BeginTransaction())
        {
            _userService.Create(dto.User);
            _companyService.Create(dto.Company);
            _context.Commit();
        }
    }
}

You can add various methods like that.