To change the IDENTITY property of a column, the column needs to be dropped and recreated

Changing an identity pk to composite key

dotnet : System.InvalidOperationException: To change the IDENTITY property of a column, the column needs to be dropped and recreated.
At line:1 char:1
+ dotnet ef migrations script
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (System.InvalidO... and recreated.:String) [], RemoteException
    + FullyQualifiedErrorId : NativeCommandError
 
   at Microsoft.EntityFrameworkCore.Migrations.SqlServerMigrationsSqlGenerator.Generate(AlterColumnOperation operation, IModel mod
el, MigrationCommandListBuilder builder)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.Generate(MigrationOperation operation, IModel model, 
MigrationCommandListBuilder builder)
   at Microsoft.EntityFrameworkCore.Migrations.MigrationsSqlGenerator.Generate(IReadOnlyList`1 operations, IModel model)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.GenerateUpSql(Migration migration)
   at Microsoft.EntityFrameworkCore.Migrations.Internal.Migrator.GenerateScript(String fromMigration, String toMigration, Boolean idempotent)
   at Microsoft.EntityFrameworkCore.Design.Internal.MigrationsOperations.ScriptMigration(String fromMigration, String toMigration, Boolean 
idempotent, String contextType)
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.ScriptMigration.<>c__DisplayClass0_1.<.ctor>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.<>c__DisplayClass3_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Design.OperationExecutor.OperationBase.Execute(Action action)

To change the IDENTITY property of a column, the column needs to be dropped and recreated.

Steps to reproduce

public class A {
 [Key]
 public int Key {get; set;}
public int Key2 {get; set; }
}
// 1. Create DB
public class A {
public int Key {get; set; }
public int Key2 {get; set; }
}
modelBuilder.Entity<A>().HasKey(e => new { e.Key, e.Key2 });
// 2. Try migrate (error message will be shown). **dotnet ef migrations script** fails as well

// **Incorrect** Migration.cs
protected override void Up(MigrationBuilder migrationBuilder)
        {
           migrationBuilder.DropPrimaryKey(
                name: "PK_A",
                table: "A");

            migrationBuilder.AlterColumn<int>(
                name: "Key",
                table: "A",
                nullable: false,
                oldClrType: typeof(int))
                .OldAnnotation("SqlServer:ValueGenerationStrategy", SqlServerValueGenerationStrategy.IdentityColumn);
}

// ** Correct** Migration.cs
protected override void Up(MigrationBuilder migrationBuilder)
        {
 migrationBuilder.DropColumn(
                name: "InfluencerId",
                table: "OfferingInfluencer",);

            migrationBuilder.AddColumn<int>(
                name: "InfluencerId",
                table: "OfferingInfluencer",
                nullable: false);
}

Can’t recall if doing schema compare in VS created the temporary table and did the data moving or not. For now I just deleted the previous data so no data migration needed to take place, but perhaps EF generates the same as Schema Compare does (or don’t 😃

Further technical details

EF Core version: 1.1.0 Database Provider: Microsoft.EntityFrameworkCore.SqlServer Operating system: Windows 10 IDE: Visual Studio Community 2017 RC