ASP.NET Core依赖注入错误:尝试激活时无法为类型解析服务 [英] ASP.NET Core Dependency Injection error: Unable to resolve service for type while attempting to activate

问题描述

我创建了一个.NET Core MVC应用程序，并使用依赖注入和存储库模式将存储库注入到控制器中.但是，我得到一个错误:

I created an .NET Core MVC application and use Dependency Injection and Repository Pattern to inject a repository to my controller. However, I am getting an error:

InvalidOperationException:尝试激活"WebApplication1.Controllers.BlogController"时，无法解析类型为"WebApplication1.Data.BloggerRepository"的服务.

InvalidOperationException: Unable to resolve service for type 'WebApplication1.Data.BloggerRepository' while attempting to activate 'WebApplication1.Controllers.BlogController'.

模型(Blog.cs)

namespace WebApplication1.Models
{
    public class Blog
    {
        public int BlogId { get; set; }
        public string Url { get; set; }
    }
}

DbContext(BloggingContext.cs)

using Microsoft.EntityFrameworkCore;
using WebApplication1.Models;

namespace WebApplication1.Data
{
    public class BloggingContext : DbContext
    {
        public BloggingContext(DbContextOptions<BloggingContext> options)
            : base(options)
        { }
        public DbSet<Blog> Blogs { get; set; }
    }
}

存储库(IBloggerRepository.cs和BloggerRepository.cs)

using System;
using System.Collections.Generic;
using WebApplication1.Models;

namespace WebApplication1.Data
{
    internal interface IBloggerRepository : IDisposable
    {
        IEnumerable<Blog> GetBlogs();

        void InsertBlog(Blog blog);

        void Save();
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using WebApplication1.Models;

namespace WebApplication1.Data
{
    public class BloggerRepository : IBloggerRepository
    {
        private readonly BloggingContext _context;

        public BloggerRepository(BloggingContext context)
        {
            _context = context;
        }

        public IEnumerable<Blog> GetBlogs()
        {
            return _context.Blogs.ToList();
        }

        public void InsertBlog(Blog blog)
        {
            _context.Blogs.Add(blog);
        }

        public void Save()
        {
            _context.SaveChanges();
        }

        private bool _disposed;

        protected virtual void Dispose(bool disposing)
        {
            if (!_disposed)
            {
                if (disposing)
                {
                    _context.Dispose();
                }
            }
            _disposed = true;
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
    }
}

Startup.cs(相关代码)

public void ConfigureServices(IServiceCollection services)
{
    // Add framework services.
    services.AddDbContext<BloggingContext>(options =>
        options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

    services.AddScoped<IBloggerRepository, BloggerRepository>();

    services.AddMvc();

    // Add application services.
    services.AddTransient<IEmailSender, AuthMessageSender>();
    services.AddTransient<ISmsSender, AuthMessageSender>();
}

控制器(BlogController.cs)

using System.Linq;
using Microsoft.AspNetCore.Mvc;
using WebApplication1.Data;
using WebApplication1.Models;

namespace WebApplication1.Controllers
{
    public class BlogController : Controller
    {
        private readonly IBloggerRepository _repository;

        public BlogController(BloggerRepository repository)
        {
            _repository = repository;
        }

        public IActionResult Index()
        {
            return View(_repository.GetBlogs().ToList());
        }

        public IActionResult Create()
        {
            return View();
        }

        [HttpPost]
        [ValidateAntiForgeryToken]
        public IActionResult Create(Blog blog)
        {
            if (ModelState.IsValid)
            {
                _repository.InsertBlog(blog);
                _repository.Save();
                return RedirectToAction("Index");
            }
            return View(blog);
        }
    }
}

我不确定自己在做什么错.有什么想法吗?

I'm not sure what I'm doing wrong. Any ideas?

推荐答案

该异常表示它无法解析WebApplication1.Data.BloggerRepository的服务，因为控制器上的构造函数正在请求具体的类而不是接口.因此，只需进行以下更改:

The exception says it cannot resolve the service for WebApplication1.Data.BloggerRepository because the constructor on your controller is asking for the concrete class instead of the interface. So just change that:

public BlogController(IBloggerRepository repository)
//                    ^
//                    Add this!
{
    _repository = repository;
}

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