EntityFramework 6.1 Add Method - entity-framework

Question

I have a very simple problem. Always use like this, but now not working, why i dont know.
I'm working on MVC 4 and Entity Framework 6.1.
I have sql table like picture below which name is Kategori,
Translation: KategoriID -> CategoryID, KategoriIsmi -> Category, UstKategoriId -> ParentCategoryID
KategoriID column has also, Primary Key and Identity Specification YES (Identity Increment 1, Seed 1)
And this is my Kategori Model class
public class Kategori
{
[Key]
public byte? KategoriID { get; set; }
[Required(ErrorMessage = "Please insert category name")]
public string KategoriIsmi { get; set; }
public byte? UstKategoriID { get; set; }
}
And my save code with EntityFramework
public void AddNewItem(Kategori item)
{
using (EmlakCMSContext _ent = new EmlakCMSContext())
{
_ent.Kategori.Add(item);
_ent.SaveChanges();
}
}
When I run this code
Income data (for save in db)
I have a error. And I write code, watch the error in IntelliTrace.
Error Translate: KategoriID alanı gereklidir -> CategoryID field is required.
But KategoriID field have set auto increment true.
How can i solve this problem? Thanks.

Answer 1

It's hard to tell as the error message is not in English. However, your primary key should not use a nullable data type. Change this:
public byte? KategoriID { get; set; }
To this:
public byte KategoriID { get; set; }
You may also need to tell entity framework that the column is an IDENTITY column:
[Key]
[DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
public byte KategoriID { get; set; }