Insert values into database- Entity Framework

Question

Why this code doesn't work? I want insert into database record with currently logged in user's UserName.

[HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> CreateMeme(Memy memy)
        {
            var user=await GetCurrentUser();
            memy.Autor = user.UserName;
            memy.Like = 0;
            memy.Dislike = 0;
            if (ModelState.IsValid)
            {
                _context.Memy.Add(memy);
                _context.SaveChanges();
                return RedirectToAction("Index");
            }

            return View(memy);
        }

This is table:

CREATE TABLE [dbo].[Memy] (
    [Id_mema] INT  IDENTITY (1, 1) NOT NULL,
    [autor]   TEXT NULL,
    [like]    INT  NULL,
    [dislike] INT  NULL,
    PRIMARY KEY CLUSTERED ([Id_mema] ASC)
);

I have 2 errors: " Cannot insert explicit value for identity column in table 'Memy' when IDENTITY_INSERT is set to OFF"

And

"An error occurred while updating the entries. See the inner exception for details"

How to resolve this?

EDIT Method CreateMeme

[HttpPost]
        [ValidateAntiForgeryToken]
        public async Task<IActionResult> CreateMeme(Memy memy)
        {
            var user=await GetCurrentUser();
            memy.Autor = user.UserName;
            memy.Like = 0;
            memy.Dislike = 0;
            if (ModelState.IsValid)
            {
                _context.Memy.Add(memy);
                _context.SaveChanges();
                return RedirectToAction("Index", "Home", new { area = "" });
            }

            return View(memy);
        }

Don't pass the identity column property to the Insert, it's telling you why it's a problem in your first error message. The database is setup to not allow custom values in your Identity column, as it appears it auto-increments. — Ryan Wilson
– Ryan Wilson, Commented Apr 10, 2019 at 18:46
When you place this line IDENTITY(1, 1) it's telling the database to add 1 to the next insert as the id_mema value, you can exclude properties from insertion in entity framework in different ways, please see this article (stackoverflow.com/questions/16340142/…) — Ryan Wilson
– Ryan Wilson, Commented Apr 10, 2019 at 18:51
Why my way is wrong? I read on other forums and it should work — kamilm758
– kamilm758, Commented Apr 10, 2019 at 19:12
Did you read the article I posted in my previous comment? Your model I'm assuming has a property which relates to the identity column in your database table, you need to tell Entity Framework not to use that property when inserting. The article I linked you to has different approaches for excluding a model property from insert. — Ryan Wilson
– Ryan Wilson, Commented Apr 10, 2019 at 19:14

Ed Mendez · Accepted Answer · 2019-04-10 22:05:46Z

1

If you are c# class to define your entities you might need to do something like this...

   public class Memy
    {
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int Id_Mema { get; set; }
        public string Autor { get; set; }

Or if you are defining your entity attributes using fluent API you might need to do something like this;

 protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Memy>()
            .Property(p => p.Id_mema)
            .ValueGeneratedOnAdd();
    }

This here should have more information on using the Fluent API and here for more information on decorating your POCOs with attributes to handle the auto-increment.

-HTH

answered Apr 10, 2019 at 22:05

Ed Mendez

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Comments

Kamal Singh · Accepted Answer · 2019-04-11 08:20:46Z

0

This error suggests the following: Your Memy table is set to 'Is Identity' = 'True' with auto increment. So you can't insert explict key values, which is logical. Please check in your function, perhaps your method parameter object in CreateMeme has a value for memy.Id_Mema.

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> CreateMeme(Memy memy)

Make sure memy.Id_Mema is not assigned by your code explicitly. Hope this helps.

answered Apr 11, 2019 at 8:20

Kamal Singh

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