实体框架按子表的最后状态选择

Question

我在以下情况下有问题。 我有这些桌子

CREATE TABLE [dbo].[TicketHistory](
[Id] [int] IDENTITY(1,1) NOT NULL,
[TicketId] [int] NOT NULL,
[TicketStateId] [int] NOT NULL,
[Created] [datetime] NOT NULL,
[UserId] [int] NOT NULL,
[Note] [ntext] NOT NULL,
CONSTRAINT [PK_TicketHistory_1] PRIMARY KEY CLUSTERED 
(
[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

和

CREATE TABLE [dbo].[Ticket](
[Id] [int] IDENTITY(1,1) NOT NULL,
[TicketTypeId] [int] NOT NULL,
[TicketSourceId] [int] NOT NULL,
[TicketCategoryId] [int] NOT NULL,
[TicketPriorityId] [int] NOT NULL,
[UserId] [int] NOT NULL,
[Created] [datetime] NOT NULL,
[UniqueCustomerId] [varchar](50) NOT NULL,
CONSTRAINT [PK_Ticket] PRIMARY KEY CLUSTERED 
(
[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

对于每个票证对象，都有一个或多个票证历史记录。

我必须选择最后一个相关票证历史记录条目具有特定状态ID的所有票证...

如何使用LINQ进行选择？

我想做这样的事情：

var a = (from t in context.Tickets 
         where t.TicketHistories.OrderBy(x => x.Id).Last().TicketStateId == 1 
         select t).ToList(); 

但是我得到这个错误：

LINQ to Entities does not recognize the method 'TicketHistory Last[TicketHistory](System.Collections.Generic.IEnumerable1[TicketHistory])' method, and this method cannot be translated into a store expression.

提前致谢 ：-）

Answer 1

尝试这个：

var a = (from t in context.Tickets 
         where (t.TicketHistories.OrderByDescending(x => x.Id)).Take(1).SingleOrDefault().TicketStateId == 1 )
         select t).ToList();