public List<CardViewModel> Retrieve()
        {
            try
            {
                List<CardViewModel> result = new List<CardViewModel>();
                using (var context = new CardHolderContext())
                {
                    result = (from crd in context.Cards
                              join cat in context.CategoryMasters on crd.CategoryId equals cat.CategoryId
                              join con in context.ContactDetails on crd.CardId equals con.CardId
                              select new CardViewModel()
                                {
                                    CardDetails = crd,
                                    Category = cat,
                                    Contact = con
                                }
                             ).ToList();
                }
                return result;
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message);
            }
        }