C＃MVC控制器在登录时中断

Question

InvalidOperationException：尝试激活“ Echelon.Controllers.SessionController”时无法解析“ Echelon.Data.IAssignmentRepository”类型的服务。

每当我尝试登录或单击导航栏中的内容时，我都会一直收到此错误，我很困惑为什么会出错，有人可以帮忙吗？ 当我开始进行电子邮件验证时，此操作开始，然后每当我尝试登录或单击任何内容时，我都会收到错误消息？

码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Authorization;
using Echelon.Models.SessionViewModels;
using Echelon.Classes;
using Microsoft.AspNetCore.Identity;
using Echelon.Models;
using Echelon.Data;

namespace Echelon.Controllers
{
    public class SessionController : Controller
    {
        StoredProcedure storedProcedure = new StoredProcedure();

        private IAssignmentRepository repository;
        private readonly AssignmentDbContext _context;

        public SessionController(IAssignmentRepository repo, AssignmentDbContext context)
        {
            repository = repo;
            _context = context;
        }

        [Authorize]
        public IActionResult Home()
        {
            return View();
        }

        public IActionResult Courses()
        {
            var Courses = storedProcedure.getCourseNames(User.Identity.Name);
            var CoursesView = new CoursesViewModel();

            foreach (var Course in Courses.ToList())
            {
                Course course = new Course();
                course.CourseName = Course;
                CoursesView.Courses.Add(course);
            }

            return View(CoursesView);
        }

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

        [HttpPost]
        public IActionResult CreateCourse(CreateCourseModel course)
        {
            if (ModelState.IsValid)
            {
                storedProcedure.addCourse(User.Identity.Name, course.CourseName, course.CourseDesc, course.StartDate, course.EndDate);
                return RedirectToAction("Courses");
            }
            else
            {
                return View();
            }
        }

        public IActionResult Assignments(string courseName)
        {
            var assignments = storedProcedure.getAssignments(User.Identity.Name, courseName);
            var AssignmentsView = new AssignmentsViewModel { CourseName = courseName };

            foreach (var Assignment in assignments.ToList())
            {
                AssignmentsView.Assignments.Add(Assignment);
            }
            return View(AssignmentsView);
        }

        public IActionResult CreateAssignment(string courseName)
        {
            CreateAssignment assignmentModel = new CreateAssignment();
            assignmentModel.CourseName = courseName;
            assignmentModel.UserName = User.Identity.Name;
            return View(assignmentModel);
        }

        [HttpPost]
        public async Task<IActionResult> CreateAssignment([Bind("AssignmentID,UserName,CourseName,AssignmentName,AssignmentDescription,TotalPoints,DueDate")] CreateAssignment assignment)
        {
            if (ModelState.IsValid)
            {
                _context.Add(assignment);
                try
                {
                    await _context.SaveChangesAsync();
                }
                catch (Exception ex)
                {
                    return View(assignment);
                }
                //return View(assignment);
                return RedirectToAction("Assignments", "Session", new { courseName = assignment.CourseName });
            }
            else
                return View(assignment);
        }

        public IActionResult Students(string courseName)
        {
            var students = storedProcedure.getStudents(User.Identity.Name, courseName);
            var studentsView = new StudentsViewModel();

            foreach (var student in students.ToList())
            {
                Student Student = new Student();
                Student.StudentFName = student.StudentFName;
                Student.StudentLName = student.StudentLName;
                Student.CourseName = student.CourseName;
                studentsView.Students.Add(Student);
            }
            return View(studentsView);
        }

        public IActionResult AllStudents()
        {
            var students = storedProcedure.getAllStudents(User.Identity.Name);
            var studentsView = new AllStudentsViewModel();

            foreach (var student in students.ToList())
                studentsView.Students.Add(student);
            return View(studentsView);
        }

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

Answer 1

当您尝试使用接口的实现时，通常会收到该错误，但尚未注册要与框架一起使用的具体实现。

如果使用的是asp.net核心使用的默认依赖项注入框架，则应在Startup.cs类的ConfigureServices方法中注册它。

services.AddTransient<IAssignmentRepository , AssignmentRepository>();

其中AssignmentRepository是您要实现IAssignmentRepository接口的具体类。

public interface IAssignmentRepository
{
    IEnumerable<CreateAssignment> Assignments { get; }
}

public class AssignmentRepository : IAssignmentRepository
{
    public IEnumerable<CreateAssignment> Assignments
    {
        get
        {
            return new List<CreateAssignment>()
            {
                new CreateAssignment(),
                new CreateAssignment()
            };
        }
    }
}

在这里，我只是硬编码了Assignments属性以返回2个CreateAssignment对象。 但是我想您可能会从数据库中读取它并返回它。

现在，当对控制器操作方法提出新请求时，框架将创建一个新的SessionController对象，并将一个AssignmentRepository对象传递给SessionController的构造函数

如果您不熟悉依赖项注入的概念，强烈建议您花16分钟的时间阅读docs.microsoft.com上的出色文档，然后再尝试编写任何其他代码。

ASP.NET Core中的依赖注入简介