Вам нужен DbFunctions
класс (System.Data.Entity
), особенно его AddYears()
метод
var requests = (from req in db.PartRequests
join info in db.UsersInfos on req.UserId equals info.aspnet_UserId
join prodName in db.Products on req.ProductId equals prodName.Id
join partRequestStatus in db.PartRequestStatus on req.PartRequestStatusId equals partRequestStatus.Id
select new ShowRequestsModel
{
WarantyExpirationDate = DbFunctions.AddYears(req.PurchasedDate, 2),
IsWarantyExpired = false
})
.Sort(sortField, sortBy);