系统InvalidOperationException：无法解析[重复]类型的服务

Question

我正在用ASP开发一个Web API。净核心。当我使用post请求执行API时，在UnitController的post方法的断点之前会引发异常。

例外

请求启动HTTP/1.1 POSThttp://localhost:5000/api/unit应用程序/json 31失败：Microsoft. AspNetCore. Server. Kestrel[13]连接ID"0HKVTL9A1LTD4"：应用程序抛出未处理的异常。系统。无效操作异常：在尝试激活“项目”时无法解析类型为“项目”的服务。DataAccess。存储库。UnitRepository'。

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

我认为问题可能在于BaseRepository和IBaseRepository之间的继承。但我不知道哪里会是我的错误。如何更正此错误？

谢谢你的帮助：），

Answer 1

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。因此：

当您在给定的类中使用DI（依赖项注入）以及IoC（控制反转）容器来规则所有依赖项（这不是必需的，但这是一种常见情况）时，您必须确保每个可注入依赖项都在容器中注册，并且-可能-这通常是一个递归问题。

Exampli gratia，查找以下伪代码：

// 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);
    }
}

Answer 2

您将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，这样可以解决问题（请原谅这个双关语）。