AutoIncrement Issue : The column cannot be modified. [ Column name = UserId ]

Question

I am currently using ASP.NET MVC4 and trying to add a new entry to a table which has an Integer as primary key. I know about the identity issue and set it to true, I also know about GUIDs but they are used for unique identifiers and not integers.

Here is where I add a new row knowing that my Primary key is a column named SheetId

if (ModelState.IsValid)
{
   var sheet = db.Sheets.Create();
   sheet.Email = Request.Cookies["UserInfo"]["Email"];
   sheet.ApprovedDays = "0000000";
   sheet.DateStarted = DateTime.Now;

   db.Sheets.Add(sheet);

   db.SaveChanges();

   return RedirectToAction("Index", "Home");
}

And this is the Sheet Model

public class Sheet
{
    [Key]
    [Required]
    public int SheetId { get; set; }
    [Required]
    public DateTime StartDate { get; set; }
    [Required]
    public string Email { get; set; }
    public string ApprovedDays { get; set; }
    //
    public virtual UserModel UserModel { get; set; }
    public virtual ICollection<Task> Task { get; set; }
}

And this is the exception I get

Exception Details: System.Data.SqlServerCe.SqlCeException: The column cannot be modified. [ Column name = SheetId ]

Answer 1

I've solved the Issue by only deleting my .EDMX Context file and Recreated it again and voilà it worked !! Thanks also for your efforts guys