DummyContext _context = new DummyContext();
            Goods goods1 = new Goods 
            {
                ID = Guid.NewGuid(),
                Name = "Пулемёт1"
            };

            Goods goods2 = new Goods
            {
                ID = Guid.NewGuid(),
                Name = "Пулемёт2"
            };
            _context.AddToGoods(goods1);
            _context.AddToGoods(goods2);
            _context.Detach(goods1);
            _context.SaveChanges();

public partial class DummyEntities : global::System.Data.Objects.ObjectContext
    {
        partial void OnContextCreated()
        {
            this.SavingChanges += new System.EventHandler(mySavingChanges);
        }
        public void mySavingChanges(object sender, System.EventArgs e)
        {
            var osm = this.ObjectStateManager;
            foreach (var entry in osm.GetObjectStateEntries(EntityState.Added | EntityState.Modified))
            {
                if (entry.Entity is Goods)
                {
                    var goods1= (Goods)entry.Entity;                    
                    this.Detach(goods1);
                }
            }
      
                

        }
    }