C# Entity Framework Core requires primary key to be defined error with existing SQL Server table with identity primary key

Question

I'm currently learning RESTful API with ASP.NET Core. I have an existing SQL Server database, with a table feedback that includes an IDENTITY(1,1) PRIMARY KEY id column.

I have the model setup as:

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Diagnostics.CodeAnalysis;

namespace Feedback_RESTful_API.Models
{
    public class Feedback
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        int Id { get; set; }
        public string Name { get; set; }
        public string Description { get; set; }
    }
}

Data as:

using Feedback_RESTful_API.Models;
using Microsoft.EntityFrameworkCore;

namespace Feedback_RESTful_API.Data
{
    public class ApiContext : DbContext
    {
        public DbSet<Feedback> Feedbacks { get; set; }

        public ApiContext(DbContextOptions<ApiContext> options) : base(options)
        {
        }
    }
}

And controller as:

using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Feedback_RESTful_API.Models;
using Feedback_RESTful_API.Data;

namespace Feedback_RESTful_API.Controllers
{
    [Route("[controller]")]
    [ApiController]
    public class FeedbackController : ControllerBase
    {
        private readonly ApiContext _context;

        public FeedbackController(ApiContext context)
        {
            _context = context;
        }

        [HttpPost]
        public JsonResult Create(Feedback feedback)
        {
            //Add the new entry
            _context.Feedbacks.Add(feedback);
            //Save the db
            _context.SaveChanges();
            //Return response
            return new JsonResult(Ok(feedback));
        }
    }
}

But when I run the app and test the POST call through Swagger UI, I get the error:

System.InvalidOperationException: The entity type 'Feedback' requires a primary key to be defined. If you intended to use a keyless entity type, call 'HasNoKey' in 'OnModelCreating'. For more information on keyless entity types, see https://go.microsoft.com/fwlink/?linkid=2141943.

I can't seem to find any solutions since most search results are in regards to inserting into the identity column, which I don't need since I just want the database server to handle it, or setting up the database/table from scratch through Entity Framework Core, which I didn't do since the database already existed in SQL Server.

Your Id column needs to be public. Typically I define them as public int Id { get; protected set; } to discourage misusing the setter. — Steve Py
– Steve Py, Commented Aug 27, 2023 at 22:57

Md. Nakibul Islam Shaki · Accepted Answer · 2023-08-27 23:09:38Z

2

In your "Feedback" class, the "Id" property is declared as private. Entity Framework requires properties to be at least protected or public in order to recognize them as part of the entity model. Change the access modifier of the "Id" property to public like this:

public class Feedback
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; } // Change access modifier to public
    public string Name { get; set; }
    public string Description { get; set; }
}

answered Aug 27, 2023 at 23:09

Md. Nakibul Islam Shaki

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