There is no argument given that corresponds to the required formal parameter 'options'

asp.net asp.net-core asp.net-core-mvc c# entity-framework-core

Question

I'm working on my first application in .Net Core.

I'm getting this build error for some reason:

Error CS7036 There is no argument given that corresponds to the required formal parameter 'options' of 'LakeViewContext.LakeViewContext(DbContextOptions<LakeViewContext>)' LakeView

I wasn't able to find a solution through Google Search or MS documentation.

My Context class:

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); 
        }
    }
}

Controller class:

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);
        }
    }
}

(bold text is underlined in Visual Studio with the same error

"private LakeViewContext db = new LakeViewContext();"

Startup class:

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();
        }
    }
}
1
4
4/21/2019 11:54:47 AM

Accepted Answer

LakeViewContext expects a DbContextOptions<LakeViewContext> to be passed into its constructor. However, you are calling the constructor without providing anything:

private LakeViewContext db = new LakeViewContext();

To fix the issue, you can just plug into the Dependency Injection system that you've set up. To do this, change your controller as follows:

public class CoursesController : Controller
{
    private readonly LakeViewContext db;

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

    ...

The ASP.NET Core Dependency Injection system will provide you with a LakeViewContext in the constructor - Just use that.

8
9/23/2017 9:14:18 PM

Popular Answer

When observing at how the classes are generated via the database first approach, I was able to fix this error with an empty constructor.

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

}



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