种子多对多EF6 Asp .NET MVC 5

Question

我看到了这个示例，但是我想先插入角色，然后将现有角色与新用户相关联 How should I seed data to many to many relation in Entity Framework Code first 5.0

    public class AbastecimentoDBInitializer : DropCreateDatabaseAlways<AbastecimentoContext>
    {
        protected override void Seed(AbastecimentoContext context)
        {
            IList<Role> roles = new List<Role>();

            roles.Add(new Role() { Id = 1, Nome = "Dev" });
            roles.Add(new Role() { Id = 2, Nome = "SuperAdmin" });
            roles.Add(new Role() { Id = 3, Nome = "Admin" });
            roles.Add(new Role() { Id = 4, Nome = "User" });

            context.Roles.AddRange(roles);

           var user1 = new User() { Id = 1, Username = "test1", Nome = "test1", Email = "test.test@test.com", IsActivo = true };
           var user2 = new User() { Id = 2, Username = "test2", Nome = "test2", Email = "test2.test2@test.com", IsActivo = true });

            base.Seed(context);
        }
    }

我创建了用户，现在如何向用户添加现有角色？