.Net 6 Unable to resolve service for type Microsoft.EntityFrameworkCore.DbSet

Question

System.InvalidOperationException: Unable to resolve service for type 'Microsoft.EntityFrameworkCore.DbSet`1[Entities.Product]' while attempting to activate 'Drin.Data.Repositories.GenericRepository`1[Entities.Product]'.

I getting this error while try to execute controller method

public class SampleDbContext : DbContext
{
    public SampleDbContext(DbContextOptions<SampleDbContext> options) : base(options) {
        
    }

    public DbSet<Category>  Category { get; set; }
    public DbSet<Product> Product { get; set; }
    public DbSet<ProductFeature> ProductFeature { get; set; }

    protected override void OnModelCreating(ModelBuilder builder)
    {
        builder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());     

        builder.Entity<ProductFeature>().HasData(
            new ProductFeature { Id = 1, Colour = "Black", Weight = 40, ProductId = 1 },
            new ProductFeature { Id = 2, Colour = "Blue", Weight = 10, ProductId = 2 });


        base.OnModelCreating(builder);
    }
}

Program.cs code file like that

builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

builder.Services.AddScoped<IUnitOfWork, UnitOfWork>();
builder.Services.AddScoped(typeof(IGenericRepository<>), typeof(GenericRepository<>));
builder.Services.AddScoped(typeof(IService<>), typeof(Service<>));
builder.Services.AddAutoMapper(typeof(MapProfile));

builder.Services.AddDbContext<SampleDbContext>(x =>
{
    x.UseSqlServer(builder.Configuration.GetConnectionString("DevConnection"), options =>
    {
        options.MigrationsAssembly(Assembly.GetAssembly(typeof(SampleDbContext)).GetName().Name);
    });
});

GenericRepository Like that also:

    public class GenericRepository<T> : IGenericRepository<T> where T : class
    {
        private readonly SampleDbContext context;
        private readonly DbSet<T> dbSet;

        public GenericRepository(SampleDbContext context, DbSet<T> dbSet)
        {
            this.context = context;
            this.dbSet = context.Set<T>();
        }

        public async Task AddAsync(T entity)
        {
            await dbSet.AddAsync(entity);
        } 
}

Answer 1

It seems that you are injecting DbSet<Product> into your repository. Usual approach is to register context only in the DI with AddDbContext or AddDbContextFactory and resolve context in the repository:

public class SomeClassDependingOnDb
{
    private readonly SomeAppDbContext _context;
    public class SomeClassDependingOnDb(SomeAppDbContext context) => _context = context;
    ... 
}

Then you can use it to access specific DbSet via generic type via Set<TEntity> method - _context.Set<TEntity> (if holding method/type is generic of TEntity ).

See more in the docs :

1. DbContext Lifetime, Configuration, and Initialization
2. Dependency injection in ASP.NET Core

UPD

Taking in account everything written earlier you repo should look like this (remove the DbSet<T> dbSet parameter):

public class GenericRepository<T> : IGenericRepository<T> where T : class
{
    private readonly SampleDbContext context;
    private readonly DbSet<T> dbSet;

    public GenericRepository(SampleDbContext context)
    {
        this.context = context;
        this.dbSet = context.Set<T>();
    }

    public async Task AddAsync(T entity)
    {
        await dbSet.AddAsync(entity);
    } 
}