Entity Framework CTP 4. "Cannot insert the value NULL into column" - Even though there is no NULL value

i have the same issue here and it's really an ugly solution.

 [Key]
public Int64 PolicyID { get; set; }

this is NOT an auto generated number

then i hit the same error.

EF Code First CTP5

after apply this:

 [Key]
 [DatabaseGenerated(DatabaseGeneratedOption.None)]
 public Int64 PolicyID { get; set; }

then it will work.

Have you tried explicitly specifying the StoreGeneratedPattern?

modelBuilder.Entity<BOB>()
    .HasKey(p => p.Id)
        .Property(p => p.Id)
            .StoreGeneratedPattern = StoreGeneratedPattern.None;

builder.Entity<BOB>().MapSingleType().ToTable("BOB");

I'm using EF 4.1, Model First and came across this problem. Here's how I solved it:

When using the Model Designer surface, when you create an Entity, you have to define a Key property, it defaults to Id, int32.

In my situation, I've chosen to use Guids for the Id, so I'd switch the int32 to Guid. But if you examine this Id after you create the entity, I saw that the Id's 'StoreGeneratedPattern' had 'identity' selected. At first I didn't think that was a problem, but when I examined the SQL being used to insert into the database, it was a bit weird in that it wasn't sending my Id. Frustrating!

But once I went back and changed the 'StoreGeneratedPattern' from 'identity' to 'none', regenerated the db and rebuilt the project, this strange message stopped happening:

Cannot insert the value NULL into column 'Id', table 'TestDB.dbo.BOB'; column does not allow nulls. INSERT fails. The statement has been terminated.

FYI - upon viewing the sql some more it seems that if you have identity chosen for StoreGeneratedPattern, the EF saves the object to the db (sans Id), then immediately fetches back the identity and saves that back to your object. i.e. this choice for StoreGeneratedPattern relies on the db to generate your Id, NOT your code!