Code first from Database - Cannot insert the value NULL into column 'Id' but value actually is not null

Question

I try to add new record :

                 entity.Id = Id;


                _bdc.EquifaxAnswers.Add(entity);

                _bdc.SaveChanges();

and Id has exactly defined as primary key and Id in code has value ( unique for table). And EF create sql code for add record:

 INSERT [dbo].[EquifaxAnswers]([FileName], [dtSend], [dtDateTime], [RecordsAll], [RecordsCorrect], 
[RecordsIncorrect], [ResendedId], [dtEmailAbout], [StartDate], [EndDate])
VALUES (@0, @1, @2, NULL, NULL, NULL, NULL, NULL, @3, @4)

And as we can see there Id does not exist, so _bdc.SaveChanges();create Exception:

Failed in 25 ms with error: Cannot insert the value NULL into column 'Id', table 'Equifax.dbo.EquifaxAnswers'; column does not allow nulls. INSERT fails.

Primary key definition:

    public partial class EquifaxAnswers
{

    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public int Id { get; set; }

Why EF don't add Id to INSERT and how to resolve this problem ?

UPD: Table definition script in database:

CREATE TABLE [dbo].[EquifaxAnswers](
[Id] [int] NOT NULL,
[FileName] [nvarchar](300) NOT NULL,
[dtSend] [datetime] NOT NULL,
[dtDateTime] [datetime] NULL,
[RecordsAll] [int] NULL,
[RecordsCorrect] [int] NULL,
[RecordsIncorrect] [int] NULL,
[ResendedId] [int] NULL,
[dtEmailAbout] [datetime] NULL,
[StartDate] [datetime] NULL,
[EndDate] [datetime] NULL,
CONSTRAINT [PK_EquifaxAnswers] PRIMARY KEY CLUSTERED 
(
[Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, 
ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

Answer 1

You have specified DatabaseGeneratedOption.None

This means that EF is not expecting the database to generate the Id field, and that you should specify the Id field yourself.

If you want the database to generate the Id field automatically, then alter the column to be an IDENTITY type, and change the code to DatabaseGeneratedOption.Identity