TempData["PaymentMethodsWithshippingMethods"]= await _paymentMethodService.FindAllWithShippingMethodsAsync();

var paymentMethodsWithshippingMethods = TempData
                .Where(x => x.Key.Contains("PaymentMethodsWithshippingMethods"))
                .Select(x => new { value = (PaymentMethodViewModel)x.Value })
                .Select(x => new PaymentMethodViewModel
                {
                    PaymentMethodId = x.value.PaymentMethodId,
                    Type = x.value.Type,
                    ShippingMethods = x.value.ShippingMethods.Select(y =>
                    new ShippingMethodViewModel
                    {
                        ShippingMethodId = y.ShippingMethodId,
                        DiscountPrice = y.DiscountPrice,
                        ProductPrice = y.ProductPrice,
                        Tax = y.Tax,
                        Type = y.Type,
                        Cost = y.Cost,
                    }).ToList()
                }).ToList();

Unable to cast object of type 'System.Collections.Generic.List`1[MeMarketShop.ViewModel.PaymentMethod.PaymentMethodViewModel]' to type 'MeMarketShop.ViewModel.PaymentMethod.PaymentMethodViewModel'.