how to apply generic multiple include with generic repository? - linq

Question

I need to make generic multiple include function as a service with generic repository.
But unfortunately, I get nothing !!
here is my attempt using aggregate linq.
public IQueryable<TEntityDTO> getRowsWithIncludeMultiple(int page = 0, params Expression<Func<TEntityDTO, object>>[] includes)
{
GridSetting gs = GetGrid();
IEnumerable<TEntity> getPage = _dbSet.Skip((page == 0 ? page : page - 1) * gs.ItemsPerPage).Take(gs.ItemsPerPage);
IQueryable<TEntityDTO> rows = _mapper.Map<IEnumerable<TEntityDTO>>(getPage).AsQueryable();
if (includes != null) { rows = includes.Aggregate(rows, (current, include) => current.Include(include)); }
// or
//foreach (var include in includes)
//{
// rows = rows.Include(include);
//}
return rows;
}
when I add debugging point I get that the includes has list of expression
and then here is how I use it
var xxx = _customerService.getRowsWithIncludeMultiple(page: 0, i => i.cityDTO, i => i.ageDTO);
the problem here I get customers without the included things (cityDTO & ageDTO)
let me include here models
public class CustomerDTO
{
public int Id { get; set; }
public string CustName { get; set; }
public string CustJobTitle { get; set; }
public string CustAge { get; set; }
public bool IsManager { get; set; }
// FKs
public int AgeId { get; set; }
public int CityId { get; set; }
public AgeDTO ageDTO { get; set; }
public CityDTO cityDTO { get; set; }
}
public class CityDTO
{
public int Id { get; set; }
public string CityName { get; set; }
public List<CustomerDTO> customerDTO { get; set; }
}
public class AgeDTO
{
public int Id { get; set; }
public int AgeName { get; set; }
public List<CustomerDTO> customerDTO { get; set; }
}
Update ... showing the whole service, usage, and injection
here is the whole generic repository service and how it looks like
public class Repository<TEntity, TEntityDTO> : IRepository<TEntity, TEntityDTO> where TEntity : class where TEntityDTO : class
{
protected readonly AppDbContext _context;
private readonly DbSet<TEntity> _dbSet;
private readonly IMapper _mapper;
public Repository(AppDbContext context, IMapper mapper)
{
_context = context;
_dbSet = context.Set<TEntity>();
_mapper = mapper;
}
// GENERIC CRUD ...
// and then here where i want to focus
public IQueryable<TEntityDTO> getRowsWithIncludeMultiple(int page = 0, params Expression<Func<TEntityDTO, object>>[] includes)
{
GridSetting gs = GetGrid();
IEnumerable<TEntity> getPage = _dbSet.Skip((page == 0 ? page : page - 1) * gs.ItemsPerPage).Take(gs.ItemsPerPage);
IQueryable<TEntityDTO> rows = _mapper.Map<IEnumerable<TEntityDTO>>(getPage).AsQueryable();
if (includes != null) { rows = includes.Aggregate(rows, (current, include) => current.Include(include)); }
// or
//foreach (var include in includes)
//{
// rows = rows.Include(include);
//}
return rows;
}
}
and then here is how customer service uses generic repo
public class CustomerService : Repository<Customer, CustomerDTO>, ICustomerService
{
public CustomerService(AppDbContext db, IMapper mapper) : base(db, mapper) { }
}
finally injection in Program.cs
builder.Services.AddScoped(typeof(IRepository<,>), typeof(Repository<,>));
builder.Services.AddScoped<ICustomerService, CustomerService>();

Answer 1

thanks #Svyatoslav Danyliv and thanks for all contributors your answer helped me a lot.
cannot apply Include to DTO object
so, I would to share what I have made so far.
instead of
public IQueryable<TEntityDTO> getRowsWithIncludeMultiple(int page = 0, params Expression<Func<TEntityDTO, object>>[] includes)
{
GridSetting gs = GetGrid();
IEnumerable<TEntity> getPage = _dbSet.Skip((page == 0 ? page : page - 1) * gs.ItemsPerPage).Take(gs.ItemsPerPage);
IQueryable<TEntityDTO> rows = _mapper.Map<IEnumerable<TEntityDTO>>(getPage).AsQueryable();
if (includes != null) { rows = includes.Aggregate(rows, (current, include) => current.Include(include)); }
return rows;
}
I applied include to the original entity not to DTO
public IEnumerable<TEntityDTO> IncludeMultiple(int page = 0, params Expression<Func<TEntity, object>>[] includes)
{
GridSetting gs = GetGrid();
IQueryable<TEntity> rows = _dbSet.Skip((page == 0 ? page : page - 1) * gs.ItemsPerPage).Take(gs.ItemsPerPage).AsQueryable();
if (includes != null)
{ rows = includes.Aggregate(rows, (current, include) => current.Include(include).AsQueryable().AsNoTracking()); }
return _mapper.Map<IEnumerable<TEntityDTO>>(rows).AsQueryable();
}
And here is some clarification to make the idea more understandable
public IEnumerable<TEntityDTO> IncludeMultiple(params Expression<Func<TEntity, object>>[] includes)
{
// get IQueryable of TEntity
IQueryable<TEntity> rows = _dbSet.AsQueryable();
// and here using `linq Aggregate` to append multiple include statement
if (includes != null)
{ rows = includes.Aggregate(rows, (current, include) => current.Include(include).AsQueryable().AsNoTracking()); }
// here I use auto mapper to map IEnumerable object to IEnumerable object as a result
return _mapper.Map<IEnumerable<TEntityDTO>>(rows).AsQueryable();
}
and finally the usage
_ServiceName.IncludeMultiple(i => i.city, i => i.age);