.NET 6激活GenericRepository时无法解析DbSet服务的问题

错误信息 #

System.InvalidOperationException: 尝试激活'Drin.Data.Repositories.GenericRepository1[Entities.Product]'时，无法解析类型为'Microsoft.EntityFrameworkCore.DbSet1[Entities.Product]'的服务。

相关代码 #

SampleDbContext代码 #

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代码 #

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代码 #

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);
    } 
}

原因分析 #

1. 依赖注入（DI）容器中未注册DbSet<T>类型的服务，而GenericRepository<T>的构造函数声明需要注入该类型，导致DI无法找到对应服务实现解析依赖。
2. 冗余设计：构造函数内部已经通过context.Set<T>()获取了DbSet<T>实例，完全没必要将DbSet<T>作为构造参数传入。

解决方法 #

修改GenericRepository<T>的构造函数，移除DbSet<T>参数，仅保留SampleDbContext注入：

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);
    } 
}

修改后，DI容器可正常解析已注册的SampleDbContext，同时仍能通过上下文获取对应DbSet<T>实例，错误即可解决。

内容的提问来源于stack exchange，提问作者mach