Entity framework core V7.0.5 problem with generated code produce Invalid Opeeration Exception

Question

I generate a controller in visual studio 2022 with the template Add API Controller with actions, using Entity Framework> The assistant generate

	public class CitiesController : Controller
    {
        private readonly ApplicationDbContext _context;

        public CitiesController(ApplicationDbContext context)
        {
            _context = context;
        }

        // GET: Cities
        public async Task<IActionResult> Index()
        {
			//return (IActionResult)await _context.Cities.ToListAsync();

			var applicationDbContext = _context.Cities.Include(c => c.Country);
			return View(await applicationDbContext.ToListAsync());
		}

I had to add

	[Route("api/[controller]/[action]")]
	[ApiController]

so that my HTTP request reach the action Index() The program halt with

I put a breakpoint on that line and applicationDbContext contain the required data fetch from the DataBase.

This code has been generated by the template What did I miss Any idea how to make it work

Answer 1

Hi,@Boucourt I reproduced the error,it has no relationship with EFCore:

I think you've got mixed WebApi app with MVC app ,If you want to retrun ViewResult with return View() You should try with a MVC app

If you just want add a scaffolded api controller in Webapi project,please try with the following options:

and the error indicates lacking required service for MVC parttern,if you insist on mixing webapi with mvc,you have to call builder.Services.AddControllersWithViews(); to regist required service in Program.cs

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RuikaiFeng

Answer 2

I found the solution Adding builder.Services.AddMvc(); in program.cs injects dependencies needed by the framework, Thank to Camilo Terevinto