在分层架构中引用 MVVM 中的实体框架

Question

My app is layered in 4 layers:

• Core : where I put some general and interface classes.
• Model : where my code-first classes, and other related to domain, such as entity configurations and repositories etc.
• Vm : where the view models live. Referencing Model .
• Desktop : where the desktop app lives. Referencing Vm .

I have installed Entity Framework into Model , ViewModel and Desktop .

My question is: is it enough to install it into Model only? Why to repeat again?

[Edit]

• Here is my implementation of Repository and UnitOfWrok ( IRepository and Repository will be on Core ):

   public interface IRepository<TEntity> where TEntity : class { TEntity Get(int id); IEnumerable<TEntity> GetAll(); IEnumerable<TEntity> Find(Expression<Func<TEntity, bool>> predicate); TEntity SingleOrDefault(Expression<Func<TEntity, bool>> predicate); void Add(TEntity entity); void AddRange(IEnumerable<TEntity> entities); void Remove(TEntity entity); void RemoveRange(IEnumerable<TEntity> entities); } public class Repository<TEntity> : IRepository<TEntity> where TEntity : class { protected readonly DbContext Context; public Repository(DbContext context) { Context = context; } public TEntity Get(int id) { return Context.Set<TEntity>().Find(id); } and so on... }

• Now, the new next interfaces and classed will be on Model

  public interface ICountryRepository : IRepository<Country> {} public class CountryRepository : Repository<Country>, ICountryRepository { public CountryRepository(CmsDbContext cmsDbContext) : base(cmsDbContext) {} } interface IUnitOfWork : IDisposable { ICountryRepository CountryRepository { get; } } public class UnitOfWork : IUnitOfWork { private readonly CmsDbContext _context; public UnitOfWork(CmsDbContext context) { _context = context; CountryRepository = new CountryRepository(_context); } public ICountryRepository CountryRepository { get; private set; } public int Commit() { return _context.SaveChanges(); } public void Dispose() { _context.Dispose(); } }

• Now, in my ViewModel

   private UnitOfWork Currentunitofwork; Currentunitofwork = new UnitOfWork(new CmsDbContext());

I followed a description of a tutor in udemy.

Is this separation correct?

Answer 1

Move all repository (Entity framework) methods behind interfaces in the Core and reference those interfaces in the ViewModel project.

Core.dll

public class SomeModel {}

public interface ISomeModelRepositoryService
{
    SomeModel GetById(int id);
    void Save(SomeModel model);
}

Model.dll - this project implements Core's interfaces and contains only database methods (Entity framework in your case)

public class SomeModelRepositoryService : ISomeModelRepositoryService
{
    public SomeModel GetById(int id)
    {
        //Entity framework code
    }

    public void Save(SomeModel model)
    {
        //Entity framework code
    }
}

ViewModel.dll

public class SomeModelViewModel
{
    private ISomeModelRepositoryService _RepositoryService;

    public SomeModel Model { get; set; }

    public SomeModelViewModel(ISomeModelRepositoryService repositoryService)
    {
        _RepositoryService = repositoryService;
    }

    public void Save()
    {
        _RepositoryService.Save(this.Model);
    }
}

Create repository implementation instances in top startUp project(Main method for example) and put it to ViewModel as parameters:

ISomeModelRepositoryService repositoryService = new SomeModelRepositoryService();

SomeModelViewModel viewmodel = new SomeModelViewModel(repositoryService);

With this approach only "Model.dll" need to have references to Entity Framework