public async Task RemovePurchaseKind(PurchaseKind purchaseKind)
        {
            var toRemove = purchaseKind.ToString();

            if (Contains(toRemove))
            {
                availablePurchaseKinds.RemoveWhere(pk => pk.p.Equals(toRemove));
            }
        }
        public async Task AddPurchaseKind(PurchaseKind purchaseKind)
        {
            var toAdd = purchaseKind.ToString();

            if (!Contains(toAdd))
            {
                availablePurchaseKinds.Add(new Prem(toAdd));
                await ProxyMarketContext.Instance.saveChanges();
            }
            ;
        }
 public bool IsAvalable(PurchaseKind purchaseKind)
 {
     return(Contains(purchaseKind.ToString()));
 }