Why is EF trying to insert NULL in id-column?

Question

I am writing my project using Entity Framework 4.0 (Model first). At the beginning of the project, I faced with this problem: I am trying to insert the filled object in the

Answer 1

Met the same problem today.

Here is how I figured out the issue.

I had added the identity seed to the column initially but after that I removed it. So I did not realize that when modifying the column definition in the Code first, the Id

Property(x => x.Id)
    .HasColumnName("Id")
    .HasColumnType("int")
    .IsRequired();

So Entity framework figured out that it was an Identity column and I got the exception above.

To fix this, I added the following:

HasDatabaseGeneratedOption(DatabaseGeneratedOption.None)

so the final piece was something like:

Property(x => x.Id)
    .HasColumnName("Id")
    .HasColumnType("int")
    .IsRequired()
    .HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);