Unable to resolve service context while attempting to activate controller when scaffolding

Question

I was doing a simple HTTP GET operation, I will display person data as JSON after hitting my url

at first, all worked

Working code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Apitest4.Models;

namespace Apitest4.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class PeopleController : ControllerBase
    {
        [HttpGet]
        public IEnumerable<Person> Get()
        {
            using (var context = new ModelContext())
            {
                return context.People.ToList();
            }
        }
    }
}

The above code you are seeing is a slightly modified version of WeatherController (Visual Studio 2019), which I was using to make my own PeopleController. This code gives me proper API response I expected

Then I wanted to do the same using an automated approach, since I have to cover a lot of tables

[Vs Code: 2019]

[Controllers(Right Click)>Add>New Sacffolded Item>Api Controller with Actions using Entity Framework]

Auto-generated Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.EntityFrameworkCore;
using Apitest4.Models;

namespace Apitest4.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class PeopleController : ControllerBase
    {

        private readonly ModelContext _context;

        public PeopleController(ModelContext context)
        {
            _context = context;
        }

        // GET: api/People
        [HttpGet]
        public async Task<ActionResult<IEnumerable<Person>>> GetPeople()
        {
            return await _context.People.ToListAsync();
        }
    }
}

This code is givine me this error:

InvalidOperationException: Unable to resolve service for type 'Apitest4.Models.ModelContext' while attempting to activate 'Apitest4.Controllers.PeopleController'.

Full error message:

image

Startup.cs

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

namespace Apitest4
{
    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.AddControllers();
        }

        // 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();
            }

            app.UseHttpsRedirection();

            app.UseRouting();

            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

Though I am new to .net, I just don't get it, Why it is not getting context properly? I didn't change any import. Please point my mistakes.

TIA

Answer 1

Be sure register your DbContext in Startup.cs like below:

services.AddDbContext<ModelContext>(options =>
                options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

Refrence:

https://learn.microsoft.com/en-us/ef/core/dbcontext-configuration/#dbcontext-in-dependency-injection-for-aspnet-core

Update:

store the connection string in appsettings.json:

"ConnectionStrings": {
    "DefaultConnection": "Server=(localdb)\\mssqllocaldb;Database=DatabaseName;Trusted_Connection=True;MultipleActiveResultSets=true"
}