.net core - unit of work generic repository pattern

Personally, i use Unit of Work to reduce a lot of dependency Injection. I can have a database Unit of work and once i use dependency Injection to inject the Database context in that Unit of work, i don't need to inject each model repository where i want to use them, but will just access the repositories from the unit of work. This also helps me only instantiate a repository only when i need it in a specific method.

public interface IDatabaseUnitOfWork
{
    DbContext DatabaseContext { get; }
    Task<bool> Save();

    IBaseRepository<UserAccount> UserAccountRepository { get; }
}

public class DatabaseUnitOfWork : IDatabaseUnitOfWork
{
    private IBaseRepository<UserAccount> _userAccountRepository;

    public DatabaseUnitOfWork(DbContext databaseContext)
    {
        DatabaseContext = databaseContext;
    }

    public DbContext DatabaseContext { get; private set; }

    public async Task<bool> Save()
    {
        try
        {
            int _save = await DatabaseContext.SaveChangesAsync();
            return await Task.FromResult(true);
        }
        catch (System.Exception e)
        {
            return await Task.FromResult(false);
        }
    }

    public IBaseRepository<UserAccount> UserAccountRepository
    {
        get
        {
            if (_userAccountRepository == null)
            {
                _userAccountRepository = new BaseRepository<UserAccount>(DatabaseContext);
            }
            return _userAccountRepository;
        }
    }
}

Then

services.AddScoped<IDatabaseUnitOfWork, DatabaseUnitOfWork>();
services.AddScoped<IServiceUnitOfWork, ServiceUnitOfWork>();

Finally

public class DemoClass
    {
        private IServiceUnitOfWork _serviceUnitOfWork;
        public DemoClass(IServiceUnitOfWork serviceUnitOfWork)
        {
            _serviceUnitOfWork = serviceUnitOfWork;
        }

        Public bool CreateUserAccount(UserAccount userAccount){
            await _serviceUnitOfWork.UserAccountRepository.Add(userAccount);
            return await _serviceUnitOfWork.Save();
        }

       ----
   }

UPDATE

GENERIC BASE REPOSITORY

public interface IBaseRepository<T> where T : class
{
    Task<bool> Add(T entity);

    Task<List<T>> GetAll();

    Task<List<T>> GetAll(params Expression<Func<T, object>>[] includes);

    Task<List<T>> SearchBy(Expression<Func<T, bool>> searchBy, params Expression<Func<T, object>>[] includes);

    Task<T> FindBy(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] includes);

    Task<bool> Update(T entity);

    Task<bool> Delete(Expression<Func<T, bool>> identity, params Expression<Func<T, object>>[] includes);

    Task<bool> Delete(T entity);

}

public class BaseRepository<T> : IBaseRepository<T> where T : class
{
    private DbContext _ctx;

    public BaseRepository(DbContext context)
    {
        _ctx = context;
    }

    public virtual async Task<bool> Add(T entity)
    {
        try
        {
            _ctx.Set<T>().Add(entity);
            return  await Task.FromResult(true);
        }
        catch (Exception e)
        {
            return  await Task.FromResult(false);
        }
    }

    public virtual async Task<List<T>> GetAll()
    {
        return _ctx.Set<T>().ToList();
    }

    public virtual async Task<List<T>> GetAll(params Expression<Func<T, object>>[] includes)
    {
        var result = _ctx.Set<T>().Where(i => true);

        foreach (var includeExpression in includes)
            result = result.Include(includeExpression);

        return await result.ToListAsync();
    }


    public virtual async Task<List<T>> SearchBy(Expression<Func<T, bool>> searchBy, params Expression<Func<T, object>>[] includes)
    {
        var result = _ctx.Set<T>().Where(searchBy);

        foreach (var includeExpression in includes)
            result = result.Include(includeExpression);

        return await result.ToListAsync();
    }

    /// <summary>
    /// Finds by predicate.
    /// http://appetere.com/post/passing-include-statements-into-a-repository
    /// </summary>
    /// <param name="predicate">The predicate.</param>
    /// <param name="includes">The includes.</param>
    /// <returns></returns>
    public virtual async Task<T> FindBy(Expression<Func<T, bool>> predicate, params Expression<Func<T, object>>[] includes)
    {
        var result = _ctx.Set<T>().Where(predicate);

        foreach (var includeExpression in includes)
            result = result.Include(includeExpression);

        return await result.FirstOrDefaultAsync();
    }

    public virtual async Task<bool> Update(T entity)
    {
        try
        {
            _ctx.Set<T>().Attach(entity);
            _ctx.Entry(entity).State = EntityState.Modified;

            return  await Task.FromResult(true);
        }
        catch (Exception e)
        {
            return  await Task.FromResult(false);
        }
    }

    public virtual async Task<bool> Delete(Expression<Func<T, bool>> identity, params Expression<Func<T, object>>[] includes)
    {
        var results = _ctx.Set<T>().Where(identity);

        foreach (var includeExpression in includes)
            results = results.Include(includeExpression);
        try
        {
            _ctx.Set<T>().RemoveRange(results);
            return  await Task.FromResult(true);
        }
        catch (Exception e)
        {
            return  await Task.FromResult(false);
        }
    }

    public virtual async Task<bool> Delete(T entity)
    {
        _ctx.Set<T>().Remove(entity);
        return await Task.FromResult(true);
    }

}

EXTENDING THE BASE REPOSITORY (eg. DeleteAllAccounts)

public interface IUserAccountRepository : IBaseRepository<UserAccount>
    {
        Task DeleteAllAccounts();
    }

    public class UserAccountRepository : BaseRepository<UserAccount>, IUserAccountRepository
    {
        private DbContext _databaseContext;
        public UserAccountRepository(DbContext databaseContext) : base(databaseContext)
        {
            _databaseContext = databaseContext;
        }

        public async Task DeleteAllAccounts()
        {
            ......
        }
    }

So instead of using _userAccountRepository = new BaseRepository<UserAccount>(DatabaseContext); you would use _userAccountRepository = new UserAccountRepository(DatabaseContext);

I'm going with a classic "it depends". Essentially DbSet<> is a repository, and DbContext is a unit of work. But that doesn't mean you can't use the repository pattern or unit of work pattern at a higher level of abstraction.

My advice is don't use it until you need it. I have used a unit or work pattern with EF Core and found it very useful in the situation where you are working with multiple DbContexts, or multiple database providers. I haven't found any other instance to use it in.

I tend not to use a generic repository ever, because I prefer to encapsulate my queries, and keep them out of my Controller or Pages.

Updated to answer the comment below:

That's a great question, and not so easily answered, and certainly out of the scope of StackOverflow.com, because craftsmanship is generally considered opinion. There's a stack exchange for questions directly related to code craftsmanship https://softwareengineering.stackexchange.com.

I will however say how excited for you I am that you are at least raising the question.

My personal opinion is to recommend 'Domain Driven Design' There are a lot of free resources on the subject, but the go to source would be the book by Eric Evans.

In essence, your business logic is the core, and all dependencies point inward. So even a 'service layer' would not have your business logic in it.