Hi :) I'm working with entity

I've asked VS to generate a DB context code gen item but get errors:

is there somewhere I need to go to to get upto date templates?

  protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            throw new UnintentionalCodeFirstException();
        }

Error    1    The type or namespace name 'DbModelBuilder' could not be found (are you missing a using directive or an assembly reference?)  

any ideas?