LINQ to Entities 无法识别选择部分中的方法

Question

我需要AddYears(2) 中的select new ShowRequestsModel。我怎样才能做到这一点？它抛出一个异常

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 = req.PurchasedDate.AddYears(2),
                    IsWarantyExpired = false
                })
                .Sort(sortField, sortBy);

Answer 1

你需要DbFunctions 类（System.Data.Entity），尤其是它的 AddYears()方法

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);