如何解决 .net core 中 Web API 构造函数中的依赖关系

Question

我是 .net 核心和依赖注入概念的新手。我想在 Web API 构造函数中注入服务接口，服务接口和实现在不同的项目中。请找到我的应用程序的以下层，

在startup.cs中，我已经添加了下面一行，

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddMvc();

    services.AddSingleton<IEntriesService, EntriesService>();
}

我的控制器，

public class EntriesController : Controller
{
    IEntriesService entryService;
    public EntriesController(IEntriesService _entryService)
    {
        entryService = _entryService;
    }

    // GET: api/values
    [HttpGet]
    public IEnumerable<string> Get()
    {
        return new string[] { "value1", "value2" };
    }
}

问题是，当我执行我的 API 应用程序时，它没有访问我的构造函数并显示如下空白页面，

没有添加构造函数，应用程序运行正常。

我的 IEntriesService，

public interface IEntriesService
{
    RepeatEntries Get(int Id);
}

我的条目服务，

public class EntriesService : IEntriesService
{
    IUnitOfWork _unitOfWork;
    public EntriesService(IUnitOfWork unitOfWork)
    {
        _unitOfWork = unitOfWork;
    }

    public bool Add(RepeatEntries entity)
    {
        _unitOfWork.EntryRepository.Add(entity);
        return true;
    }
}

我的 IUnitOfWork，

public interface IUnitOfWork : IDisposable
{
    IEntriesRepository EntryRepository { get; }
    void Complete();
}

我的工作单位，

public class UnitOfWork : IUnitOfWork
{
    private readonly IEntriesRepository _entryRepository;
    public UnitOfWork(IEntriesRepository entryRepository)
    {
        _entryRepository = entryRepository;
    }

    public IEntriesRepository EntryRepository
    {
        get
        {
            return _entryRepository;
        }
    }

    void IUnitOfWork.Complete()
    {
        throw new NotImplementedException();
    }

    #region IDisposable Support
    private bool disposedValue = false; // To detect redundant calls



    protected virtual void Dispose(bool disposing)
    {
        if (!disposedValue)
        {
            if (disposing)
            {
                // TODO: dispose managed state (managed objects).
            }

            // TODO: free unmanaged resources (unmanaged objects) and override a finalizer below.
            // TODO: set large fields to null.

            disposedValue = true;
        }
    }

    // TODO: override a finalizer only if Dispose(bool disposing) above has code to free unmanaged resources.
    // ~UnitOfWork() {
    //   // Do not change this code. Put cleanup code in Dispose(bool disposing) above.
    //   Dispose(false);
    // }

    // This code added to correctly implement the disposable pattern.
    void IDisposable.Dispose()
    {
        // Do not change this code. Put cleanup code in Dispose(bool disposing) above.
        Dispose(true);
        // TODO: uncomment the following line if the finalizer is overridden above.
        // GC.SuppressFinalize(this);
    }
    #endregion
}

我还需要添加什么才能使其正常工作？有可能还是我需要改变我的方法？

Answer 1

您必须使用组合根注册所有依赖项，确保使用正确的生命周期注册它们，即：(Scoped, Transient, Singleton) 以避免出现问题未来。

public void ConfigureServices(IServiceCollection services) {
    // Add framework services.
    services.AddMvc();

    services.AddSingleton<IEntriesService, EntriesService>();
    services.AddTransient<IUnitOfWork, UnitOfWork>();
    services.AddTransient<IEntriesRepository, EntriesRepository>();
    services.AddSingleton<IConnectionFactory, ConnectionFactory>();

    //...add other dependencies. 
}

花点时间查看文档：

Introduction to Dependency Injection in ASP.NET Core

如何解决 .net core 中 Web API 构造函数中的依赖关系

How to resolve dependency in Web API constructor in .net core

c#

dependency-injection

asp.net-core-mvc

asp.net-core

asp.net-core-webapi