Question

我正在尝试将LINQ转换为SQL从C＃转换为F＃。这就是我想出来的：

let get (roles : List<string>) = 
                                query {
                                    for t in db.Tabs do
                                    join r in db.Regions on (t.Id = r.FkTab)
                                    join l in db.Links on (r.Id = l.FkRegion)
                                    where (roles.Contains(l.Role) || roles.Contains("Administrator"))
                                    groupValBy (t,r,l) (t.Id, t.Label) into tt
                                    select {
                                        Label = snd tt.Key;
                                        Regions =  query {
                                                             for xr in db.Regions do
                                                             join xl in db.Links on (xr.Id = xl.FkRegion)
                                                             where (xr.FkTab.Equals (fst tt.Key) && (roles.Contains(xl.Role) || roles.Contains("Administrator")))
                                                             groupValBy (xr, xl) (xr.Id, xr.Label) into rr
                                                             select {
                                                                     Label = snd rr.Key;
                                                                     Links = query {
                                                                                 for yl in db.Links do
                                                                                 where (yl.FkRegion.Equals (fst rr.Key) && (roles.Contains(yl.Role) || roles.Contains("Administrator")))
                                                                                 select {
                                                                                         Label = yl.Label;
                                                                                         Url = yl.Url;
                                                                                         Role = yl.Role
                                                                                 }
                                                                             } |> Seq.toList
                                                            } 
                                                    } |> Seq.toList
                                    }
                                } |> Seq.toList

而不是我使用过记录的类，这里是：

type Link = {Url : string; Role : string; Label : string}

type Region = {Label : string; Links : List<Link>}

type Tab = {Label : string; Regions : List<Region> }

不幸的是我在运行时遇到异常：

A first chance exception of type 'System.NotSupportedException' occurred in System.Data.Linq.dll

消息是：System.NotSupportedException：不支持查询运算符'AsQueryable'。

我对F＃非常环保，我错过了什么？也许我不能在LINQ to SQL中使用记录？我不能以那种方式筑巢？

由于

编辑： db是数据库上下文：

let db = SqlConnection.GetDataContext()

如果你想在家里试试这个，这里是创建所需三个表的脚本：

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[Links](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [fkRegion] [int] NOT NULL,
    [label] [varchar](50) NOT NULL,
    [role] [varchar](50) NOT NULL,
    [url] [varchar](100) NOT NULL,
 CONSTRAINT [PK_Links] 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]

GO
SET ANSI_PADDING OFF
GO
/****** Object:  Table [dbo].[Regions]    Script Date: 22/08/2015 12:06:49 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[Regions](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [fkTab] [int] NOT NULL,
    [label] [varchar](50) NOT NULL,
 CONSTRAINT [PK_Regions] 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]

GO
SET ANSI_PADDING OFF
GO
/****** Object:  Table [dbo].[Tabs]    Script Date: 22/08/2015 12:06:49 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[Tabs](
    [id] [int] IDENTITY(1,1) NOT NULL,
    [label] [varchar](50) NOT NULL,
 CONSTRAINT [PK_Tabs] 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]

GO
SET ANSI_PADDING OFF
GO
ALTER TABLE [dbo].[Links]  WITH CHECK ADD  CONSTRAINT [FK_Links_Regions] FOREIGN KEY([fkRegion])
REFERENCES [dbo].[Regions] ([id])
GO
ALTER TABLE [dbo].[Links] CHECK CONSTRAINT [FK_Links_Regions]
GO
ALTER TABLE [dbo].[Regions]  WITH CHECK ADD  CONSTRAINT [FK_Regions_Tabs] FOREIGN KEY([fkTab])
REFERENCES [dbo].[Tabs] ([id])
GO
ALTER TABLE [dbo].[Regions] CHECK CONSTRAINT [FK_Regions_Tabs]
GO

EDIT2：问题似乎与查询的结果有关。我尝试将记录类型更改为IEnumerable并删除Seq.toList。但是，每当我尝试对可枚举的任何操作时，都会弹出相同的异常，例如， Model.Count（）（其中Model是IEnumerable）。帮助

F＃LINQ to SQL：System.NotSupportedException：不支持查询运算符'AsQueryable'

0 个答案: