Unable to resolve service for type in .NET 5 with entity framework scaffolding

Question

Hi I am trying to do a website using .NET 5 with some entity framework 3.1.21.

I get this error on my Comments/index page

I read an article on the Microsoft docs I'm pretty sure about this error but I can't find it now.

can anyone point me in the right direction?

thanks in advance,

    InvalidOperationException: Unable to resolve service for type 'EC.DataAccess.EF.Context.EcContext' while attempting 
InvalidOperationInvalidOperationException: Unable to resolve service for type 'EC.DataAccess.EF.Context.ECContext' while attempting to activate 'EC09.Controllers.CommentsController'.InvalidOperationException: Unable to resolve service for type 'EC.DataAccess.EF.Context.ECContext' while attempting to activate 'EC09.Controllers.CommentsController'.

Answer 1

Hi @DMO

In the Startup ConfigureServices method, you should register the database context like this:

public void ConfigureServices(IServiceCollection services)
{
    services.AddControllersWithViews();

    services.AddDbContext<EcContext>(options =>
    options.UseSqlServer(Configuration.GetConnectionString("EcContextconnectionstring")));
}

You can set the connection string in the appsettings.json file:

"ConnectionStrings": {
  "EcContextconnectionstring": "Server=(localdb)\\mssqllocaldb;Database=MvcMovieContext-2;Trusted_Connection=True;MultipleActiveResultSets=true"
}

And the database context as below:

    public class EcContext : DbContext
    {
        public EcContext (DbContextOptions<EcContext> options)
            : base(options)
        {
        }

        public DbSet<Movie> Movie { get; set; }
    }

More detail information, refer to the following tutorials:

Part 4, add a model to an ASP.NET Core MVC app

Part 5, work with a database in an ASP.NET Core MVC app

Tutorial: Get started with EF Core in an ASP.NET MVC web app

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Best regards,

Dillion

Answer 2

EF 3.1 is EOL. You need to update to at least EF 6. .NET 5 is also EOL and you need to update to .NET 6 (or 7).

Once you've upgraded then ensure that you're calling AddDbContext when configuring your app services at startup. This will register your DbContext and then you can use it as a parameter to your CommentsController constructor.

//Sample startup
...
services.AddDbContext<EcContext>(options => {
   options.UseSqlServer("your connection string");
});

//You can now use EcContext in constructors
public class CommentsController : Controller
{
   public CommentsController ( EcContext context )   
   {   
      _context = context;
   }

   private readonly EcContext _context;
}

Answer 3

Does .NET 6 use the startup file? can you add that statement to the program.cs?

Answer 4

this is my Startup.cs file so far. I haven't edited it yet. it's just the default auto generated stuff

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace EC09
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
        }

        //My stuff
        //public void ConfigureServices(IServiceCollection services)
        //{
        //    //modify the ForumManageContext to your generated dbcontext model
        //    services.AddDbContext<ForumManageContext>();

        //    services.AddRazorPages();
        //}

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }
            app.UseHttpsRedirection();
            app.UseStaticFiles();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }
}

Answer 5

Hey that actually worked. thanks very much.