private SizeSingleton()
 {
     repository = new SizeRepository(DbContextSingleton.Instance.Context);
     Sizes      = repository.GetList();
     _sizes.Add(typeof(SmallSize), new SmallSize());
     _sizes.Add(typeof(MediumSize), new MediumSize());
     _sizes.Add(typeof(LargeSize), new LargeSize());
 }