c# - 具有通用服务和存储库代码的 .NET Core 依赖注入(inject)错误

Question

我正在尝试将我在所有项目中的 .NET 框架中使用的通用代码模板移动到 .NET Core，并且在 .NET Core 中的依赖注入(inject)时遇到了一些问题。
这是我的代码:
API Controller :

[Route("api/[controller]")]
[ApiController]
public class ProductController : ControllerBase
{
    private readonly IProductService _productService;

    public ProductController(IProductService productService)
    {
        _productService = productService;
    }

    [HttpGet]
    public IActionResult GetAll()
    {
        var products = _productService.GetAll();

        return Ok(products);
    }
}

产品服务:

public class ProductService : ServiceBase<Product, BaseRepository<Product>>, IProductService
{
    public ProductService(BaseRepository<Product> rep) : base(rep)
    {
    }
}

产品服务:

public interface IProductService : IServiceBase<Product>
{
}

服务基础:

public interface IServiceBase<TEntity>
{
    IEnumerable<TEntity> GetAll();
}

服务基地:

public abstract class ServiceBase<TEntity, TRepository> : IServiceBase<TEntity>
        where TEntity : class
        where TRepository : BaseRepository<TEntity>
{
    public TRepository Repository;

    public ServiceBase(BaseRepository<TEntity> rep)
    {
        Repository = (TRepository)rep;
    }

    public IEnumerable<TEntity> GetAll()
    {
        return Repository.GetAll();
    }
}

基础存储库:

public class BaseRepository<T> : IBaseRepository<T> where T : class
{
    private readonly DatabaseContext _dbContext;

    public BaseRepository(DatabaseContext dbContext)
    {
        _dbContext = dbContext;
    }

    public IEnumerable<T> GetAll()
    {
        return _dbContext.Set<T>();
    }
}

IBase 存储库:

public interface IBaseRepository<T> where T : class
{
    IEnumerable<T> GetAll();
}

数据库上下文:

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

    public DbSet<Product> Products { get; set; }
}

启动文件:

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<DatabaseContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"),
            x => x.MigrationsAssembly("AdministrationPortal.Data")));

        services.AddTransient<IProductService, ProductService>();

        services.AddControllers();
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();

        app.UseRouting();

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

当我尝试使用 F5(或绿色播放按钮)启动 API 项目时出现错误:

System.AggregateException: 'Some services are not able to be constructed (Error while validating the service descriptor 'ServiceType: AdministrationPortal.Interfaces.Services.IProductService Lifetime: Transient ImplementationType: AdministrationPortal.Core.Services.ProductService': Unable to resolve service for type 'AdministrationPortal.Repositories.Repositories.BaseRepository`1[AdministrationPortal.Domain.Entities.Product]' while attempting to activate 'AdministrationPortal.Core.Services.ProductService'.)'

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Answer 1

您的 ProductService类正在尝试解决 BaseRepository<Product> 的依赖关系，但您尚未在服务提供商中注册。在您的 Startup类，您可以简单地注册该类型，它应该可以工作:

public void ConfigureServices(IServiceCollection services)
{
    services.AddDbContext<DatabaseContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection"),
        x => x.MigrationsAssembly("AdministrationPortal.Data")));

    services.AddTransient<IProductService, ProductService>();
    services.AddTransient<BaseRepository<Product>>(); // <----- This is needed

    services.AddControllers();
}

或者，您可以注册 BaseRepository<>作为一个开放的泛型，它将使用它给出的任何类型来解决:

services.AddTransient(typeof(BaseRepository<>));