Question

我正在研究.Net Core中的第一个应用程序。

由于某种原因我收到了这个构建错误：

错误CS7036没有给出符合所需形式参数＆＃39;选项＆＃39; ＆＃39; LakeViewContext.LakeViewContext（DbContextOptions＆lt; LakeViewContext＆gt;）＆＃39;湖景

我无法通过Google搜索或MS文档找到解决方案。

我的上下文类：

using LakeView.Models;
using Microsoft.EntityFrameworkCore;

namespace LakeView
{
    public class LakeViewContext : DbContext
    {
        public LakeViewContext(DbContextOptions<LakeViewContext> options) : base(options)
        {

        }

        public DbSet<HTMLElement> HTMLElements { get; set; }
        public DbSet<CustomizedElement> CustomizedElements { get; set; }
        public DbSet<TemplateFileType> TemplateFileTypes { get; set; }
        public DbSet<StyleFile> StyleFiles { get; set; }
        public DbSet<Template> Templates { get; set; }
        public DbSet<Course> Courses { get; set; }
        public DbSet<Page> Pages { get; set; }
        public DbSet<HTML> HTMLs { get; set; }
        public DbSet<Comment> Comments { get; set; }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<CustomizedElementTemplate>()
                .HasKey(s => new { s.CustomizedElementId, s.TemplateId });
            base.OnModelCreating(modelBuilder); 
        }
    }
}

控制器类：

using LakeView.Models;
using LakeView.Models.ViewModels;
using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;
using System.Linq;

namespace LakeView.Controllers
{
    public class CoursesController : Controller
    {

        private LakeViewContext db = new LakeViewContext();

        public IActionResult Index()
        {
            ICollection<Course> courses = db.Courses.ToList();
            return View(courses);
        }

        [HttpGet]
        public IActionResult CreateCourse()
        {
            return View("CreateCourse");
        }

        [HttpPost]
        [ValidateAntiForgeryToken]
        public IActionResult CreateCourse(CreateCourseViewModel courseVM)
        {
            if (ModelState.IsValid)
            {
                Course newCourse = new Course()
                {
                    CourseCode = courseVM.CourseCode,
                    CourseTitle = courseVM.CourseTitle,
                    MasterOU = int.Parse(courseVM.MasterOU)
                };

                db.Courses.Add(newCourse);
                db.SaveChanges();

                return RedirectToAction("Index");

            }
                return View("CreateCourse", courseVM);
        }
    }
}

（粗体文本在Visual Studio中带有下划线并带有相同的错误

＆＃34;私有LakeViewContext db = new LakeViewContext （）;＆＃34;

启动课程：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using LakeView.Models;

namespace LakeView
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc();
            var connection = @"Data Source = (localdb)\MSSQLLocalDB; Database = LakeViewData; Trusted_Connection = True;";
            services.AddDbContext<LakeViewContext>(options => options.UseSqlServer(connection));
        }

        // 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();

            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            app.UseStaticFiles();

            app.UseMvcWithDefaultRoute();
        }
    }
}

Answer 1

LakeViewContext期望将DbContextOptions<LakeViewContext>传递给其构造函数。但是，您在不提供任何内容的情况下调用构造函数：

private LakeViewContext db = new LakeViewContext();

要解决此问题，您只需插入已设置的依赖注入系统即可。为此，请按如下方式更改控制器：

public class CoursesController : Controller
{
    private readonly LakeViewContext db;

    public CoursesController(LakeVieContext db)
    {
        this.db = db;
    }

    ...

ASP.NET核心依赖注入系统将在构造函数中为您提供LakeViewContext - 只需使用它。

Answer 2

您正在尝试在控制器中新建dbcontext而不传递选项。

您应该在控制器中添加一个构造函数，并将dbContext添加到构造函数中，以便它被注入，即

public CoursesController(LakeViewContext dbContext)
{

   db = dbContext;

}
private LakeViewContext db;
... the rest of your code

依赖注入会将它传递给你

Answer 3

在观察如何通过数据库第一种方法生成类时，我能够使用空的构造函数来修复此错误。

public class MyDBContext : DbContext
{
    public MyDBContext()
    {
    }
//Rest of your code

}

没有任何论据符合所要求的形式参数＆＃39;选项＆＃39;

3 个答案: