Entity framework migration how to seed data from previous table - entity-framework

Question

I have a column of type time that I need to change to type bigint.
As I see it, the only way is to drop the column and create a new one with a bigint type.
For that I will run the following migration :
public partial class Migration1 : DbMigration
{
public override void Up()
{
DropColumn("dbo.MyDurations", "Duration");
AddColumn("dbo.MyDurations", "Duration", c => c.Long(nullable: false));
}
public override void Down()
{
DropColumn("dbo.MyDurations", "Duration");
AddColumn("dbo.MyDurations", "Duration", c => c.Time(nullable: false, precision: 7));
}
}
How can I get the data from the current column in time type and seed it to the new one by transforming it with TimeSpan.Ticks(duration) ?
From what I understood, I can only seed data from the Seed(DbContext ctx) function from the Configuration file. But the seed method is run after the migration.
Is it possible to access data before applying migration, then apply the migration and then seed the data ?

Answer 1

You can run your own Sql in a migration using the Sql method. You need to change your migration to something like this:
public override void Up()
{
AddColumn("dbo.MyDurations", "NewDuration", c => c.Long(nullable: false));
Sql("UPDATE dbo.MyDurations SET NewDuration = Duration");
DropColumn("dbo.MyDurations", "Duration");
RenameColumn("dbo.MyDurations", "NewDuration", "Duration");
}