InvalidOperationException: Sequence contains no matching element
at System.Linq.Enumerable.First[TSource](IEnumerable`1 source, Func`2 predicate) at MaxShop.UI.Models.Product.ProductViewModel.get_DefautSelectedSize() at MaxShop.UI.Models.Product.ProductViewModel.<>c__DisplayClass1.b__0(ProductDetailStatusSkuViewModel x) at System.Linq.Enumerable.FirstOrDefault[TSource](IEnumerable`1 source, Func`2 predicate) at MaxShop.UI.Models.Product.ProductViewModel.get_DefaultSelectedSkuId()