Int32/Int64 properties with default value automatically annotated with SqlServerValueGenerationStrategy.IdentityColumn in migration

[sergeitemkin]

After migrating to EF7 RC2 we've noticed that our int and long properties that are set with HasDefaultValue in the ModelBuilder are causing the migration script to annotate columns representing those properties with an identity attribute. This, in turn, causes an exception since defaults cannot be created on identity columns.

Here's a simplified example of the DbContext:

    public class Entity
    {
        public Guid Id { get; set; }
        public int Column1 { get; set; }
    }

    public class TestContext : DbContext
    {
        public DbSet<Entity> Entitys { get; set; }

        public TestContext() { }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            var serverName = @"localhost";
            var dbName = "Test";

            optionsBuilder
                .UseSqlServer($"data source={serverName};initial catalog={dbName};Integrated Security=true;");
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Entity>(entity =>
            {
                entity
                    .Property(e => e.Column1)
                    .HasDefaultValue(1);
            });
        }
    }

    static void Main(string[] args)
    {
        using (var context = new TestContext())
        {
            context.Database.EnsureCreated();
        }
    }

When creating a migration with Add-Migration, I get the following, which causes an exception when context.Database.EnsureCreated is called (Defaults cannot be created on columns with an IDENTITY attribute. Table 'Entitys', column 'Column1'):

    protected override void Up(MigrationBuilder migrationBuilder)
    {
        migrationBuilder.CreateTable(
            name: "Entitys",
            columns: table => new
            {
                Id = table.Column<Guid>(nullable: false),
                Column1 = table.Column<int>(nullable: false, defaultValue: 1)
                    .Annotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn)
            },
            constraints: table =>
            {
                table.PrimaryKey("PK_Entitys", x => x.Id);
            });
    }

Is there something I'm missing, or is there a workaround for this?

[rowanmiller]

"Identity pattern" is a more general concept in EF that means a value is generated for the property for new entities. For example, your Guid Id property is also setup as Identity in the model, since the values are generated for new entities. This is also true for default values, we need to get the values that was generated back from the database when the row is inserted (more obvious when the default is something like GETDATE() rather than a constant of 1).

Looks like an issue in migrations, where the presence of a default value means we shouldn't be trying to also use SQL Server IDENTITY to also handle value generation.

[julianpaulozzi]

+1

[rowanmiller]

As a workaround for this issue, you should remove the .Annotation(...) call in the scaffolded migration. Obviously that's just a workaround and we'll get this issue fixed for RTM.