System.InvalidOperationException: 无法解析服务类型

Question

我正在使用 ASP.NET 核心开发 Web API。当我使用 post 请求执行我的 API 时，在 UnitController 的 Post 方法中的断点之前抛出异常。

异常

Request starting HTTP/1.1 POST http://localhost:5000/api/unit application/json 31 fail: Microsoft.AspNetCore.Server.Kestrel[13] Connection id "0HKVTL9A1LTD4": An unhandled exception was thrown by the application. System.InvalidOperationException: Unable to resolve service for type 'Project.DataAccess.Repository.UnitRepository' while attempting to activate 'Project.Service.UnitService'.

上下文

namespace Project.DataAccess.Library.Interface {
public interface IBaseRepository<M> where M : class, IEntity
{
    IEnumerable<M> SelectAll();

    M SelectByID(int id);

    void Insert(M obj);

    void Update(M obj);

    void Delete(int id);

    void Save();
}
}

namespace Project.DataAccess.Library {
public abstract class BaseRepository<M> : IBaseRepository<M> where M : class, IEntity
{
    protected ProjectContext Db { get; }
    private DbSet<M> table = null;

    protected DbSet<M> Table
    {
        get
        {
            return this.table;
        }
    }

    public BaseRepository(ProjectContext dbContext)
    {
        Db = dbContext;
        this.table = Db.Set<M>();
    }

    public void Delete(int id)
    {
        M existing = this.SelectByID(id);
        if (existing != null)
            this.table.Remove(existing);
    }

    // others methods
}
}

namespace Project.DataAccess.Repository
{
    public class UnitRepository : BaseRepository<Unit>, IUnitRepository
    {
        public UnitRepository(Projectcontext) : base(context) { }
    }
}

namespace Project.Service
{
    public class UnitService : BaseService<Unit>, IUnitService
    {
        public UnitService(UnitRepository unitRepository) : base(unitRepository) { }
    }
}


namespace AssoManager.Service.Library
{
    public abstract class BaseService<M> : IBaseService<M> where M : class, IEntity
    {
        private IBaseRepository<M> _repository;

        public BaseService(IBaseRepository<M> repository)
        {
            _repository = repository;
        }

        public IEnumerable<M> GetAll()
        {
            return this._repository.SelectAll();
        }
    }
 }


namespace Project
{
    public class Startup
    {
        public Startup(IHostingEnvironment env)
        {
            var builder = new ConfigurationBuilder()
                .SetBasePath(env.ContentRootPath)
                .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
                .AddEnvironmentVariables();
            Configuration = builder.Build();
        }

        public IConfigurationRoot Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            // Add framework services.
            services.AddMvc();

            this.DataAccessMySqlConfiguration(services);
            this.ConfigureRepository(services);
            this.ConfigureServicesUnit(services);
            this.ConfigureServicesUser(services);
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();

            app.UseMvc();
        }

        #region Database configuration

        public void DataAccessMySqlConfiguration(IServiceCollection services)
        {
            services.AddDbContext<ProjectContext>(options => options.UseMySQL(Configuration.GetConnectionString("MsSQLConnection")));
        }

        #endregion

        #region DataAccess configuration

        public void ConfigureRepository(IServiceCollection services)
        {
            services.AddScoped<IUnitRepository, UnitRepository>();
            services.AddScoped<IUserRepository, UserRepository>();
        }

        #endregion

        #region Services configuration

        /// <summary>
        /// Is used to add unit services to the container
        /// </summary>
        public void ConfigureServicesUnit(IServiceCollection services)
        {
            services.AddTransient<IUnitService, UnitService>();
            services.AddTransient<IMeetingService, MeetingService>();
        }

        /// <summary>
        /// Is used to add user services to the container
        /// </summary>
        public void ConfigureServicesUser(IServiceCollection services)
        {
            services.AddTransient<IUserService, UserService>();
        }

        #endregion Services configuration
    }
}


namespace Project.Controllers
{
    [Route("api/[controller]")]
    public class UnitController : Controller
    {
        private IUnitService UnitService;

        public UnitController(IUnitService unitService)
        {
            UnitService = unitService;
        }

        // GET api/units
        [HttpGet]
        public IEnumerable<Unit> Get()
        {
            return UnitService.GetAll();
        }

        // GET api/unit/5
        [HttpGet("{id}")]
        public IActionResult Get(int id)
        {
            Unit unit;
            //->Check
            if (id < 1)
                return BadRequest();
            //->Processing
            unit = UnitService.GetByID(id);
            if (unit == null)
                return NotFound();
            return new ObjectResult(unit);
        }

        // POST api/unit
        [HttpPost]
        public IActionResult Post([FromBody]Unit unit)
        {
            //->Check
            if (unit == null)
                return BadRequest();
            //->Processing
            UnitService.Create(unit);
            return CreatedAtRoute("Get", new { id = unit.Id }, unit);
        }

        // PUT api/unit/5
        [HttpPut("{id}")]
        public void Put(int id, [FromBody]string value)
        {
        }

        // DELETE api/unit/5
        [HttpDelete("{id}")]
        public void Delete(int id)
        {
        }
    }
}

版本

"dependencies": {
    "Microsoft.NETCore.App": {
      "version": "1.0.0",
      "type": "platform"
    },
    "Microsoft.AspNetCore.Mvc": "1.0.0",
    "Microsoft.AspNetCore.Server.Kestrel": "1.0.0",
    "Microsoft.Extensions.Configuration.EnvironmentVariables": "1.0.0",
    "Microsoft.Extensions.Configuration.FileExtensions": "1.0.0",
    "Microsoft.Extensions.Configuration.Json": "1.0.0",
    "Microsoft.Extensions.Logging": "1.0.0",
    "Microsoft.Extensions.Logging.Console": "1.0.0",
    "Microsoft.Extensions.Logging.Debug": "1.0.0",
    "Microsoft.Extensions.Options.ConfigurationExtensions": "1.0.0",
    "Microsoft.EntityFrameworkCore": "1.0.0",
    "MySql.Data.Core": "7.0.4-IR-191",
    "MySql.Data.EntityFrameworkCore": "7.0.4-IR-191",
    "IdentityServer4": "1.0.0-rc2",
    "AssoManager.Domain": "1.0.0-*",
    "AssoManager.Service": "1.0.0-*",
    "AssoManager.DataAccess": "1.0.0-*"
  },

问题

我认为问题可能出在 BaseRepository 和 IBaseRepository 之间的继承上。但我不明白我的错误在哪里。我该如何纠正这个错误？

感谢您的帮助:),

Answer 1

您正在将 UnitRepository 注册为 IUnitRepository，但请求您的 IoC 解析 UnitRepository。它没有注册，所以它失败了。

尝试让 UnitService 使用 IUnitRepository 而不是 UnitRepository，这应该可以解决问题（请原谅双关语）。

Answer 2

我发现 Callum Bradbury 的答案非常有用（谢谢你，Callum），但我认为更一般的答案可能适用于不同的情况。所以：

当你在给定的 class 中使用 DI（依赖注入），以及 IoC（控制反转）容器来控制所有的依赖（这不是必需的，但这是常见的情况），您必须确定，每个可注入依赖项都已在容器中注册，并且 - 可能 - 这通常是一个递归问题。

Exempli gratia，寻找以下 pseudo-code：

// A class which uses injected dependencies
class NeedSomeDependeciesToBeInjected
{
    public NeedSomeDependeciesToBeInjected (
        IThisIsReallyImportant important,
        IThisIsUsefulButNotImportant useful) {}
}

// A complex dependency, which requires other injected dependency
// (So, yes, recursion...)
class ThisIsReallyImportant : IThisIsReallyImportant
{
    public ThisIsReallyImportant (
        IThisIsRequiredToBecomeImportant required) {}
}

// A dependency, which does not require other injected dependency,
// but is required for another dependency
class ThisIsRequiredToBecomeImportant : IThisIsRequiredToBecomeImportant 
{
    public ThisIsRequiredToBecomeImportant () {}
}

// A simple dependency, which does not require other injected dependency,
// and is not required for others
class ThisIsUsefulButNotImportant : IThisIsUsefulButNotImportant
{
    public ThisIsUsefulButNotImportant () {}
}

class Program
{
    private readonly WeaponOfChoiceInIoC container;

    public void ConfigureDependencies()
    {
        container = new WeaponOfChoiceInIoC();

        container.Register(IThisIsRequiredToBecomeImportant,
            ThisIsRequiredToBecomeImportant);
        container.Register(IThisIsReallyImportant,
            ThisIsReallyImportant );
        container.Register(IThisIsUsefulButNotImportant,
            ThisIsUsefulButNotImportant );
    }

    public void MethodToPlayWithDependencies()
    {
        var toy = container.GetInstance(NeedSomeDependeciesToBeInjected);
    }
}

System.InvalidOperationException: 无法解析服务类型

System.InvalidOperationException: Unable to resolve service for type

c#

dependency-injection

.net-core

asp.net-core

asp.net-core-webapi