var comments = (from p in _ctx.CommentRottas
.Where(s => s.Rotta_Id == Id && s.Status == 1)
.Include(s => s.Client)
orderby p.Date descending
select new CommentDTO
{
CommentId = p.Id,
Rotta = new RottaDTO
{
RottaId = p.Rotta_Id,
RottaDate = p.SU_ROUTES.Date,
ClientId = p.SU_ROUTES.ClientId,
COMMENTS_NUM = p.SU_ROUTES.COMMENTS_NUM,
LIKES_NUM = p.SU_ROUTES.LIKES_NUM,
},
Client = new ClientDTO
{
Id = p.Client_Id,
UserName = p.Client.UserName,
Profile_Image = p.Client.Profile_Image,
},
CommentDate = p.Date,
Comment = p.comment,
}
)
.ToList();
return comments;
编辑：添加了数据库值
ID RID评论UID DATE
107 680 test 27 2017-08-24 10：49：41.583 1
108 680 gdfg 27 2017-08-24 10：50：06.630 1
109 681 Khgs gdlkdg 18 2017-08-24 12：08：01.793 1
110 680 ttt 27 2017-08-24 13：24：52.407 1
111 684 dasdasd 27 2017-08-24 13：32：22.997 1
112 680 fdsfs 27 2017-08-24 13：59：24.317 1
113 684 OK 27 2017-08-25 07：35：43.627 1
114 684 Ghfgjn 20 2017-08-25 13：43：15.020 1
来自RID 684查询的结果：
[
{
"CommentId": 111,
"CommentDate": "2017-08-24T13:32:22.997",
"Comment": "dasdasd",
"Client": {
"Id": 27,
"UserName": "Test",
"Profile_Image": "https://rota2.blob.core.windows.net/profile-images/profile.png"
},
"Station": null,
"Rotta": {
"RottaId": 684,
"RottaDate": "2017-08-24T13:30:40.51",
"COMMENTS_NUM": 3,
"LIKES_NUM": 2,
"Completed": 0,
"STATUS": 0,
"Is_Started": null,
"ClientId": 19,
"Stations": null,
"Client": null
},
"Media": null
},
{
"CommentId": 114,
"CommentDate": "2017-08-25T13:43:15.02",
"Comment": "Ghfgjn",
"Client": {
"Id": 20,
"UserName": "Besart2",
"Profile_Image": "https://rota2.blob.core.windows.net/profile-images/Date-2017-08-28T08-06-21-User-20.jpg"
},
"Station": null,
"Rotta": {
"RottaId": 684,
"RottaDate": "2017-08-24T13:30:40.51",
"COMMENTS_NUM": 3,
"LIKES_NUM": 2,
"Completed": 0,
"STATUS": 0,
"Is_Started": null,
"ClientId": 19,
"Stations": null,
"Client": null
},
"Media": null
},
{
"CommentId": 113,
"CommentDate": "2017-08-25T07:35:43.627",
"Comment": "OK",
"Client": {
"Id": 27,
"UserName": "Test",
"Profile_Image": "https://rota2.blob.core.windows.net/profile-images/profile.png"
},
"Station": null,
"Rotta": {
"RottaId": 684,
"RottaDate": "2017-08-24T13:30:40.51",
"COMMENTS_NUM": 3,
"LIKES_NUM": 2,
"Completed": 0,
"STATUS": 0,
"Is_Started": null,
"ClientId": 19,
"Stations": null,
"Client": null
},
"Media": null
}
]
GO
/****** Object: Table [dbo].[CommentRottas] Script Date: 8/28/2017 7:14:59 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[CommentRottas](
[Id] [bigint] IDENTITY(1,1) NOT NULL,
[Rotta_Id] [bigint] NOT NULL,
[comment] [nvarchar](500) NULL,
[Client_Id] [int] NOT NULL,
[Date] [datetime] NOT NULL,
[Status] [int] NOT NULL,
CONSTRAINT [PK_dbo.CommentRottas] PRIMARY KEY CLUSTERED
(
[Id] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON)
)
GO
ALTER TABLE [dbo].[CommentRottas] WITH CHECK ADD CONSTRAINT [FK_dbo.CommentRottas_dbo.SU_ROUTES_Rotta_Id] FOREIGN KEY([Rotta_Id])
REFERENCES [dbo].[SU_ROUTES] ([ROUTE_ID])
ON DELETE CASCADE
GO
ALTER TABLE [dbo].[CommentRottas] CHECK CONSTRAINT [FK_dbo.CommentRottas_dbo.SU_ROUTES_Rotta_Id]
GO
我终于解决了问题。我不知道是什么原因引起了问题但是返回对象而不是DTO解决了问题。这是我的解决方案。
public ICollection<Object> GetRouteComments(long Id)
{
/*
var result = await _ctx.CommentRottas
.Where(s => s.Rotta_Id == Id)
.Include(s => s.Client)
.Where(s => s.Status == 1)
.OrderByDescending(p => p.Date)
.ToListAsync();
*/
var comments = (from p in _ctx.CommentRottas
.Where(s => s.Rotta_Id == Id && s.Status == 1)
.Include(s => s.Client)
orderby p.Date descending
select new CommentDTO
{
CommentId = p.Id,
Rotta = new RottaDTO
{
RottaId = p.Rotta_Id,
RottaDate = p.SU_ROUTES.Date,
ClientId = p.SU_ROUTES.ClientId,
COMMENTS_NUM = p.SU_ROUTES.COMMENTS_NUM,
LIKES_NUM = p.SU_ROUTES.LIKES_NUM,
},
Client = new ClientDTO
{
Id = p.Client_Id,
UserName = p.Client.UserName,
Profile_Image = p.Client.Profile_Image,
},
CommentDate = p.Date,
Comment = p.comment,
}
)
.ToList().Cast<Object>().ToList();
return comments;
答案 0 :(得分：0)
您是否尝试过选择后.OrderBy而不是之前？
答案 1 :(得分：0)
如果它可以为空，请尝试命令p.Date.GetDefaultOrValue（）
答案 2 :(得分：0)
我找到了解决方案，但我不确定它为什么会起作用。
public ICollection<Object> GetRouteComments(long Id)
{
/*
var result = await _ctx.CommentRottas
.Where(s => s.Rotta_Id == Id)
.Include(s => s.Client)
.Where(s => s.Status == 1)
.OrderByDescending(p => p.Date)
.ToListAsync();
*/
var comments = (from p in _ctx.CommentRottas
.Where(s => s.Rotta_Id == Id && s.Status == 1)
.Include(s => s.Client)
orderby p.Date descending
select new CommentDTO
{
CommentId = p.Id,
Rotta = new RottaDTO
{
RottaId = p.Rotta_Id,
RottaDate = p.SU_ROUTES.Date,
ClientId = p.SU_ROUTES.ClientId,
COMMENTS_NUM = p.SU_ROUTES.COMMENTS_NUM,
LIKES_NUM = p.SU_ROUTES.LIKES_NUM,
},
Client = new ClientDTO
{
Id = p.Client_Id,
UserName = p.Client.UserName,
Profile_Image = p.Client.Profile_Image,
},
CommentDate = p.Date,
Comment = p.comment,
}
)
.ToList().Cast<Object>().ToList();
return comments;
答案 3 :(得分：0)
将它转换为List两次是浪费计算时间。此外，如果您只使用包含结果的某些部分，请不要包含。实体框架将知道要查询的列。
说完了。我认为你的问题是由于方法语法和查询语法的混合。也许加一些额外的括号会有所帮助。
我已将您的查询翻译成方法语法，并使用了您的输入。输出符合预期。
int Id = 684;
var result = myDbContext.CommentRottas
.Where(comment => comment.Id == Id && comment.Status == 1)
.OrderByDescending(comment => comment.Date)
.Select(comment => new CommentDTO()
{
CommentId = comment.Id,
Rotta = new RottaDTO
{
RottaId = comment.Rotta_Id,
// not tested all properties
},
Client = new ClientDTO()
{
Id = comment.Client_Id,
// not tested all properties
},
CommentDate = comment.Date,
Comment = comment.Comment,
})
.ToList();
这有效并提供预期的顺序。所以我的建议是坚持一种语法：方法或查询。如果使用查询语法，请使用括号。
最后：考虑不返回列表，而是IEnumerable。如果您的调用者只想要第一个元素，或者前几个元素，那么查询所有元素将是一个浪费。让你的调用者决定是否要在枚举之前将其他函数添加到IEnumerable（或将其放入列表中）