C#•5mo ago

Certain services could not be instantiated due to iss

Hi , I am trying implement Unit of Work design pattern.

C#  public class Repository<T> : IRepository<T> where T : class
 {
     protected readonly DbContext _context;
     protected readonly DbSet<T> _dbSet;
     protected readonly ILogger _logger;
     public Repository(DbContext context, ILogger logger)
     {
         _context = context;
         _dbSet = context.Set<T>();
         _logger = logger;
     }

     public virtual async Task<T?> GetByIdAsync(int id)
     {
         var data = await _dbSet.FindAsync(id);

         if (data == null) { return null; }
         else { return data; }
     }

     public virtual async Task<IEnumerable<T>> GetAllAsync()
     {
         return await _dbSet.ToListAsync();
     }

     public virtual async Task AddAsync(IEnumerable<T> entities)
     {
         await _dbSet.AddRangeAsync(entities);
         await _context.SaveChangesAsync();
     }

     public virtual async Task UpdateAsync(IEnumerable<T> entities)
     {
         _dbSet.UpdateRange(entities);
         await _context.SaveChangesAsync();
     }

    
 }    

 public class DepartmentRepository : Repository<Department>, IDepartmentRepository
 {
      private readonly DbContext _context;
     public DepartmentRepository(DbContext context, ILogger logger) : base(context, logger)
     {
       _context = context;
     }


     public override async Task<IEnumerable<Department>> GetAllAsync()
     {
         try
         {
             var result = await _dbSet.Where(x => x.IsActive == true).ToListAsync();
             return result.AsEnumerable();
         }
         catch (Exception ex)
         {
             _logger.LogError((ex), "{Repo} GetAllAsync ", typeof(DepartmentRepository));
             return null;
         }
     }
 }  

Program.cs
             builder.Services.AddScoped<IDepartmentRepository, DepartmentRepository>();

C#  public class Repository<T> : IRepository<T> where T : class
 {
     protected readonly DbContext _context;
     protected readonly DbSet<T> _dbSet;
     protected readonly ILogger _logger;
     public Repository(DbContext context, ILogger logger)
     {
         _context = context;
         _dbSet = context.Set<T>();
         _logger = logger;
     }

     public virtual async Task<T?> GetByIdAsync(int id)
     {
         var data = await _dbSet.FindAsync(id);

         if (data == null) { return null; }
         else { return data; }
     }

     public virtual async Task<IEnumerable<T>> GetAllAsync()
     {
         return await _dbSet.ToListAsync();
     }

     public virtual async Task AddAsync(IEnumerable<T> entities)
     {
         await _dbSet.AddRangeAsync(entities);
         await _context.SaveChangesAsync();
     }

     public virtual async Task UpdateAsync(IEnumerable<T> entities)
     {
         _dbSet.UpdateRange(entities);
         await _context.SaveChangesAsync();
     }

    
 }    

 public class DepartmentRepository : Repository<Department>, IDepartmentRepository
 {
      private readonly DbContext _context;
     public DepartmentRepository(DbContext context, ILogger logger) : base(context, logger)
     {
       _context = context;
     }


     public override async Task<IEnumerable<Department>> GetAllAsync()
     {
         try
         {
             var result = await _dbSet.Where(x => x.IsActive == true).ToListAsync();
             return result.AsEnumerable();
         }
         catch (Exception ex)
         {
             _logger.LogError((ex), "{Repo} GetAllAsync ", typeof(DepartmentRepository));
             return null;
         }
     }
 }  

Program.cs
             builder.Services.AddScoped<IDepartmentRepository, DepartmentRepository>();

I am unable to locate the mistake here. Could someone please guide me here?

16 Replies

Pobiega•5mo ago

are you sure you always resolve this as IDepartmentRepository? do you have the actual error message?

N0b0dyOP•5mo ago

@Pobiega

System.AggregateException: 'Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: UserServices.Interface.IDepartmentRepository Lifetime: Scoped ImplementationType: UserServices.Repositories.DepartmentRepository': Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbContext' while attempting to activate 'UserServices.Repositories.DepartmentRepository'.)'

System.AggregateException: 'Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: UserServices.Interface.IDepartmentRepository Lifetime: Scoped ImplementationType: UserServices.Repositories.DepartmentRepository': Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbContext' while attempting to activate 'UserServices.Repositories.DepartmentRepository'.)'

this is actual error mesage

Pobiega•5mo ago

Ah you should probably not request a DbContext in your repository it should be your actual repository err actual context the services.AddDbContext<YourContextType>(); line adds your context to the DI its THAT type you need to request

N0b0dyOP•5mo ago

 builder.Services.AddDbContext<ApplicationDbContext>(options =>
 options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

 builder.Services.AddDbContext<ApplicationDbContext>(options =>
 options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

Already added that line and removed dbcontext from the repo. But same error.

Pobiega•5mo ago

wdym cant be show new DepartmentRepository source

N0b0dyOP•5mo ago

DepartmentRepository...

Pobiega•5mo ago

look at your constructor still requesting a DbContext and not ApplicationDbContext

N0b0dyOP•5mo ago

this is my base class

BaseRepository.cs

N0b0dyOP•5mo ago

is the base class has any problem?

Pobiega•5mo ago

no, thats fine now. I feel I should mention that this is a bit redundant thou EF already implements Unit of Work AND repository patterns so you are just wrapping a UoW in another UoW

N0b0dyOP•5mo ago

little bit lost here. could you please elaborate more? i do not need base class repo here?

Pobiega•5mo ago

Well, look at what methods are available on DbSet<T> and see what your code does

 public virtual async Task AddAsync(IEnumerable<T> entities)
        {
            await _dbSet.AddRangeAsync(entities);
            await _context.SaveChangesAsync();
        }

 public virtual async Task AddAsync(IEnumerable<T> entities)
        {
            await _dbSet.AddRangeAsync(entities);
            await _context.SaveChangesAsync();
        }

you are literally just calling an existing method, then calling save changes

N0b0dyOP•5mo ago

make sense

Pobiega•5mo ago

DbSet<T> is a generic repository over T already and guess what ApplicationDbContext is? its your unit of work 🙂 So what I'm trying to say is, if you are just doing this to learn how UOW/repo works, go ahead but please do not actually wrap EFCore with UoW/Repo in a real codebase, because its superfluent UoW/repo makes a lot more sense if you are wrapping a raw database connection, or some other source, but not EF/EFCore

N0b0dyOP•5mo ago

thanks for the help. it makes a lot of sense.

Gaming

Programming

Certain services could not be instantiated due to iss