Question

我在Db中有一个类型为decimal的列，它也可以为空。我想要的是，如果它为null，则显示0.0。为此，我正在尝试遵循我的LINQ声明：

CostPerUnit = od.CostPerUnit == null ? "0.0": od.CostPerUnit

哪个出错：

Error   9   Type of conditional expression cannot be determined because there is no implicit conversion between 'string' and 'decimal'

也为ref提供了完整声明：

var rmas = (
                    from o in db.Orders
                    join od in db.OrderDetails on o.OrderNumber equals od.OrderNumber
                    join r in db.RMAs on o.OrderNumber equals r.OrderNumber
                    join rd in db.RMADetails on r.RMANumber equals rd.RMANumber
                    where (rd.WrongSKU == od.SKU)
                    join i in db.Inventory on od.SKU equals i.LocalSKU into grp
                    from g in grp.DefaultIfEmpty()
                    select new
                    {
                        r.RMANumber
                                    ,
                        r.Reason
                                    ,
                        o.Name
                                    ,
                        o.Company
                                    ,
                        o.Address
                                    ,
                        o.Address2
                                    ,
                        o.City,
                        o.State
                                    ,
                        o.Country
                                    ,
                        o.Email
                                    ,
                        o.Zip
                                    ,
                        o.Phone
                                    ,
                        o.ShipName,
                        o.ShipCompany
                                    ,
                        o.ShipAddress
                                    ,
                        o.ShipAddress2
                                    ,
                        o.ShipCity
                                    ,
                        o.ShipCountry
                                    ,
                        o.ShipState
                                    ,
                        o.ShipPhone
                                    ,
                        o.ShipZip

                                    ,
                        o.OrderNumber
                                    ,
                        o.ShippingTotal
                                    ,
                        o.BalanceDue
                                    ,
                        r.Status
                                    ,
                        OrderDate = o.OrderDate
                                    ,
                        DateIssued = r.DateIssued
                                    ,
                        SerialNumbers = rd.SerialNumbers ?? ""
                                    ,
                        o.SourceOrderID
                                    ,
                        od.SKU
                                    ,
                        od.ItemNumber
                                    ,
                        QTYOrdered = od.QuantityOrdered
                                    ,
                        od.QuantityReturned
                                    ,
                        rd.QuantityAuthorized
                                    ,
                        RMA_ItemNumber1 = rd.ItemNumber
                                    ,
                        rd.Price
                                    ,
                        rd.WrongSKU
                                    ,
                        g.Text1
                                    ,

                        CostPerUnit = od.CostPerUnit == null ? "0.0": od.CostPerUnit

                    }
                ).Take(50).ToList();

Answer 1

你应该做的是

CostPerUnit = od.CostPerUnit ?? 0.0m

这使用Null Coalescing运算符。它专门用于为可空类型添加默认值

您可以做的是

CostPerUnit = od.CostPerUnit == null ? 0.0m : od.CostPerUnit.Value

注意.Value属性。它得到了十进制的非可空版本。

您可能打算做的是

CostPerUnit = od.CostPerUnit == null ? "0.0": od.CostPerUnit.Value.ToString()

这将使CostPerUnit成为一个字符串

如何在LINQ中选择Nullable十进制类型？

1 个答案: