使用匿名类型——一个变量选择两个不同的查询
本文关键字:两个 查询 选择 变量 一个 类型 | 更新日期: 2023-09-27 18:01:58
我想变量取两个查询之一,但有两个不同的表,我有错误"条件表达式的类型无法确定,因为System.Linq.IQueryable<WGamesTicket>
和System.Linq.IQueryable<AllGamesTicket>
之间没有隐式转换
var dsakj = (type == "mix") ?
(from el in objDC.WGamesTickets
where el.ticket.time == DTtemp
//&& el.typeOfGame == "mix"
select el)
:
(from el in objDC.AllGamesTickets
where el.ticket.time == DTtemp
//&& el.typeOfGame == "eng"
select el);
您必须转换为一个新的自定义类。例如,您正在从两个不同的表中提取数据,但可能希望从每个表中收集id和名称。因此将代码改为:
var dsakj = (type == "mix") ?
(from el in objDC.WGamesTickets
where el.ticket.time == DTtemp
//&& el.typeOfGame == "mix"
select new myCustomObject()
{
id = el.id,
name = el.name,
})
:
(from el in objDC.AllGamesTickets
where el.ticket.time == DTtemp
//&& el.typeOfGame == "eng"
select new myCustomObject()
{
id = el.id,
name = el.name,
});
查询的结果是不同类型的,您的第一个是IQueryable<WGamesTickets>
,第二个是IQueryable<AllGamesTickets>
。因此,不能确定"var"变量dsakj
的类型。
你可以投影到一个共同的类类型:
var dsakj = (type == "mix") ?
(from el in objDC.WGamesTickets
where el.ticket.time == DTtemp
//&& el.typeOfGame == "mix"
select new GameTicket() { Type = el.typeOfGame} )
:
(from el in objDC.AllGamesTickets
where el.ticket.time == DTtemp
//&& el.typeOfGame == "eng"
select new GameTicket() { Type = el.typeOfGame} ));
这样做的缺点是您必须"手动"将属性复制到新的GameTicket
类实例中。