C#依赖注入错误：某些服务无法被实例化

编程语言 2026-07-11

我在启动我的应用时遇到了以下错误：

System.AggregateException: '某些服务无法被构造（在验证服务描述符时出错 'ServiceType: BestPractice.ExtendedServiceNamespace.IExtendedService4[BestPractice.Inputs.ExtendedCreateInput,BestPractice.Inputs.ExtendedUpdateInput,BestPractice.Database.ExtendedComponent,System.Guid] Lifetime: Scoped ImplementationType: BestPractice.ExtendedServiceNamespace.ExtendedService4[BestPractice.Inputs.ExtendedCreateInput,BestPractice.Database.ExtendedComponent,BestPractice.Inputs.ExtendedUpdateInput,System.Guid]': 无法解析类型 'BestPractice.Database.IEntityRepository2[BestPractice.Database.ComponentBase,System.Guid]' while attempting to activate 'BestPractice.ExtendedServiceNamespace.ExtendedService4[BestPractice.Inputs.ExtendedCreateInput,BestPractice.Database.ExtendedComponent,BestPractice.Inputs.ExtendedUpdateInput,System.Guid]'.)'

我要注入的服务是这样的：我有一个服务接口，以及一个实现该接口的具体实现。

using BestPractice.Database;
using BestPractice.Inputs;

namespace BestPractice.ExtendedServiceNamespace;

public interface IExtendedService <TCreateInput, TUpdateInput, TEntity, TEntityId>
    where TCreateInput : CreateBaseInput
    where TUpdateInput : UpdateBaseInput
    where TEntity : ComponentBase 

{

    public TEntity Create(TCreateInput input);

    public Task<ComponentBase> UpdateAsync(TEntityId id, TUpdateInput input);
}


public class ExtendedService <TCreateInput, TEntity, TUpdateBaseInput, TEntityId> : 
    IExtendedService <TCreateInput, TUpdateBaseInput, TEntity, TEntityId> 
    where TCreateInput : CreateBaseInput 
    where TEntity : ComponentBase 
    where TUpdateBaseInput : UpdateBaseInput
{
    IEntityRepository<ComponentBase, TEntityId> _repository;

    public ExtendedService(IEntityRepository<ComponentBase, TEntityId> repository)
    {
        _repository = repository;
    }

    public virtual TEntity Create(TCreateInput input) 
    {
        TEntity component;
        component = Activator.CreateInstance(typeof(TEntity)) as TEntity ?? throw new InvalidOperationException("Component entity could not be constructed");
        component.test1 = input.test1;
        component.test2 = input.test2;
        component.test3 = input.test3;
        _repository.Add(component);
        return component;
    }

    public virtual async Task<ComponentBase> UpdateAsync(TEntityId id, TUpdateBaseInput input)
    {
        var component = await _repository.FindByIdOrFailAsync(id);
        await UpdateBaseValues(component, input);
        return component;
    }

    protected async Task UpdateBaseValues(ComponentBase component, UpdateBaseInput input)
    {
    }

}

使用该服务的类是：BaseController

using BestPractice.Database;
using BestPractice.Exceptions;
using BestPractice.ExtendedServiceNamespace;
using BestPractice.Factory;
using BestPractice.Inputs;
using BestPractice.Outputs;
using BestPractice.Utilities;
using Microsoft.AspNetCore.Mvc;
using System.Net;

namespace BestPractice.Controllers;

public class BaseController<
    TEntity, 
    TEntityId, 
    TObject, 
    TCreateInput, 
    TUpdateInput
    > : ControllerBase
    where TEntity : ComponentBase

    where TObject : BaseObject
    where TCreateInput : CreateBaseInput
    where TUpdateInput : UpdateBaseInput
{
    protected readonly IEntityRepository<TEntity , TEntityId> _entityRepository;
    protected readonly IExtendedService<TCreateInput, TUpdateInput, TEntity, TEntityId> _service;
    protected readonly IComponentFactory<TEntity, TObject> _factory;

    public BaseController(
        IEntityRepository<TEntity, TEntityId> repository,
        IExtendedService<TCreateInput, TUpdateInput, TEntity, TEntityId> service,
        IComponentFactory<TEntity, TObject> factory)
    {
        _entityRepository = repository;
        _service = service;
        _factory = factory;
    }

    [NonAction]
    public virtual IActionResult Create(TCreateInput input)
    {
        try
        {
            TEntity component;
            component = _service.Create(input);
            return Ok(ApiResponseHelper.CreateSuccessResponse(_factory.Make(component)));
        }
        catch (EntityAlreadyExistsException ex)
        {
            ApiResponse<dynamic> response = ApiResponseHelper.CreateErrorResponse(HttpStatusCode.Conflict, ex.Message, ex);
            return Conflict(response);
        }
        // return new EmptyResult();
    }
}

我在我的 program.cs 文件中注册了该服务

builder.Services.AddScoped<IExtendedService<ExtendedCreateInput, ExtendedUpdateInput, ExtendedComponent, Guid>, ExtendedService<ExtendedCreateInput, ExtendedComponent, ExtendedUpdateInput, Guid>>();

如果有解释如何正确注册该服务的解答，我将不胜感激。

解决方案

为了让你的服务在处理任意泛型参数时能够被解析，你需要在注册时不指定泛型类型参数：

builder.Services.AddTransient(typeof(IExtendedService<,,,>), typeof(ExtendedService<,,,>));

然而，当我尝试使用 IExtendedService 解析该类时，仍然遇到错误。

解决方法是在 ExtendedService 类中正确排序泛型类型参数

public class ExtendedService<TCreateInput, TUpdateBaseInput, TEntity, TEntityId>
// not
// public class ExtendedService<TCreateInput, TEntity, TUpdateBaseInput, TEntityId>

error