属于某个角色的用户列表（Any的用法）
使用Subsonic，我们有两种方法获取属于某个角色的用户列表，分别是表关联和子查询。
Subsonic的表关联实现：
// 查询 X_User 表
SqlQuery q = new Select().From<XUser>().InnerJoin(XRoleUser.UserIdColumn, XUser.IdColumn);
q.Where("1").IsEqualTo("1"); // 在用户名称中搜索
string searchText = ttbSearchUser.Text.Trim();
if (!String.IsNullOrEmpty(searchText))
{
q.And(XUser.NameColumn).ContainsString(searchText);
} // 过滤选中角色下的所有用户
object[] values = Grid1.DataKeys[Grid1.SelectedRowIndexArray[0]];
int roleId = Convert.ToInt32(values[0]);
q.And(XRoleUser.RoleIdColumn).IsEqualTo(roleId); // 在查询添加之后，排序和分页之前获取总记录数
// Grid1总共有多少条记录
Grid2.RecordCount = q.GetRecordCount(); // 排列
q.OrderBys.Add(GetSortExpression(Grid2, XUser.Schema)); // 数据库分页
q.Paged(Grid2.PageIndex + 1, Grid2.PageSize);
XUserCollection items = q.ExecuteAsCollection<XUserCollection>(); Grid2.DataSource = items;
Grid2.DataBind();
Subsonic的子查询实现：
// 查询 X_User 表
SqlQuery q = new Select().From<XUser>();
q.Where("1").IsEqualTo("1"); // 在用户名称中搜索
string searchText = ttbSearchUser.Text.Trim();
if (!String.IsNullOrEmpty(searchText))
{
q.And(XUser.NameColumn).ContainsString(searchText);
} // 过滤选中角色下的所有用户
object[] values = Grid1.DataKeys[Grid1.SelectedRowIndexArray[0]];
int roleId = Convert.ToInt32(values[0]);
SqlQuery subQ = new Select(XRoleUser.UserIdColumn).From<XRoleUser>().Where(XRoleUser.RoleIdColumn).IsEqualTo(roleId); q.And(XUser.IdColumn).In(subQ); // 在查询添加之后，排序和分页之前获取总记录数
// Grid1总共有多少条记录
Grid2.RecordCount = q.GetRecordCount(); // 排列
q.OrderBys.Add(GetSortExpression(Grid2, XUser.Schema)); // 数据库分页
q.Paged(Grid2.PageIndex + 1, Grid2.PageSize);
XUserCollection items = q.ExecuteAsCollection<XUserCollection>(); Grid2.DataSource = items;
Grid2.DataBind();
使用Entity Framework就不能从数据库的角度思考问题，而应该从实体类之间的关系考虑问题，具体的实现：
IQueryable<User> q = DB.Users; // 在用户名称中搜索
string searchText = ttbSearchUser.Text.Trim();
if (!String.IsNullOrEmpty(searchText))
{
q = q.Where(u => u.Name.Contains(searchText));
} // 过滤选中角色下的所有用户
object[] values = Grid1.DataKeys[Grid1.SelectedRowIndexArray[0]];
int roleId = Convert.ToInt32(values[0]);
q = q.Where(u => u.Roles.Any(r => r.ID == roleId)); // 在查询添加之后，排序和分页之前获取总记录数
Grid2.RecordCount = q.Count(); // 排列和分页
q = SortAndPage<User>(q, Grid2); Grid2.DataSource = q;
Grid2.DataBind();
这里用到了 Any 方法，可以这么理解：检索一些用户，只要用户的任意一个角色是roleId就可以。
来看下生成的SQL语句：
exec sp_executesql N'SELECT TOP (20)
[Project2].[ID] AS [ID],
[Project2].[Name] AS [Name],
[Project2].[Email] AS [Email],
[Project2].[Password] AS [Password],
[Project2].[Enabled] AS [Enabled],
[Project2].[Gender] AS [Gender],
[Project2].[ChineseName] AS [ChineseName],
[Project2].[EnglishName] AS [EnglishName],
[Project2].[Photo] AS [Photo],
[Project2].[QQ] AS [QQ],
[Project2].[CompanyEmail] AS [CompanyEmail],
[Project2].[OfficePhone] AS [OfficePhone],
[Project2].[OfficePhoneExt] AS [OfficePhoneExt],
[Project2].[HomePhone] AS [HomePhone],
[Project2].[CellPhone] AS [CellPhone],
[Project2].[Address] AS [Address],
[Project2].[Remark] AS [Remark],
[Project2].[IdentityCard] AS [IdentityCard],
[Project2].[Birthday] AS [Birthday],
[Project2].[TakeOfficeTime] AS [TakeOfficeTime],
[Project2].[LastLoginTime] AS [LastLoginTime],
[Project2].[CreateTime] AS [CreateTime],
[Project2].[DeptID] AS [DeptID]
FROM ( SELECT [Project2].[ID] AS [ID], [Project2].[Name] AS [Name], [Project2].[Email] AS [Email], [Project2].[Password] AS [Password], [Project2].[Enabled] AS [Enabled], [Project2].[Gender] AS [Gender], [Project2].[ChineseName] AS [ChineseName], [Project2].[EnglishName] AS [EnglishName], [Project2].[Photo] AS [Photo], [Project2].[QQ] AS [QQ], [Project2].[CompanyEmail] AS [CompanyEmail], [Project2].[OfficePhone] AS [OfficePhone], [Project2].[OfficePhoneExt] AS [OfficePhoneExt], [Project2].[HomePhone] AS [HomePhone], [Project2].[CellPhone] AS [CellPhone], [Project2].[Address] AS [Address], [Project2].[Remark] AS [Remark], [Project2].[IdentityCard] AS [IdentityCard], [Project2].[Birthday] AS [Birthday], [Project2].[TakeOfficeTime] AS [TakeOfficeTime], [Project2].[LastLoginTime] AS [LastLoginTime], [Project2].[CreateTime] AS [CreateTime], [Project2].[DeptID] AS [DeptID], row_number() OVER (ORDER BY [Project2].[Name] DESC) AS [row_number]
FROM ( SELECT
[Extent1].[ID] AS [ID],
[Extent1].[Name] AS [Name],
[Extent1].[Email] AS [Email],
[Extent1].[Password] AS [Password],
[Extent1].[Enabled] AS [Enabled],
[Extent1].[Gender] AS [Gender],
[Extent1].[ChineseName] AS [ChineseName],
[Extent1].[EnglishName] AS [EnglishName],
[Extent1].[Photo] AS [Photo],
[Extent1].[QQ] AS [QQ],
[Extent1].[CompanyEmail] AS [CompanyEmail],
[Extent1].[OfficePhone] AS [OfficePhone],
[Extent1].[OfficePhoneExt] AS [OfficePhoneExt],
[Extent1].[HomePhone] AS [HomePhone],
[Extent1].[CellPhone] AS [CellPhone],
[Extent1].[Address] AS [Address],
[Extent1].[Remark] AS [Remark],
[Extent1].[IdentityCard] AS [IdentityCard],
[Extent1].[Birthday] AS [Birthday],
[Extent1].[TakeOfficeTime] AS [TakeOfficeTime],
[Extent1].[LastLoginTime] AS [LastLoginTime],
[Extent1].[CreateTime] AS [CreateTime],
[Extent1].[DeptID] AS [DeptID]
FROM [dbo].[Users] AS [Extent1]
WHERE (N''admin'' <> [Extent1].[Name]) AND ( EXISTS (SELECT
1 AS [C1]
FROM [dbo].[RoleUsers] AS [Extent2]
WHERE ([Extent1].[ID] = [Extent2].[UserID]) AND ([Extent2].[RoleID] = @p__linq__0)
))
) AS [Project2]
) AS [Project2]
WHERE [Project2].[row_number] > 0
ORDER BY [Project2].[Name] DESC',N'@p__linq__0 int',@p__linq__0=1
go
EF生成的SQL语句是很复杂，我们来稍微简化一下（为了看清本质，去掉了排序，过滤以及返回字段的个数等）：
exec sp_executesql N'SELECT [Project2].[ID] AS [ID], [Project2].[Name] AS [Name], [Project2].[Email] AS [Email], [Project2].[Password] AS [Password]
FROM ( SELECT
[Extent1].[ID] AS [ID],
[Extent1].[Name] AS [Name],
[Extent1].[Email] AS [Email],
[Extent1].[Password] AS [Password]
FROM [dbo].[Users] AS [Extent1]
WHERE (N''admin'' <> [Extent1].[Name]) AND ( EXISTS (SELECT
1 AS [C1]
FROM [dbo].[RoleUsers] AS [Extent2]
WHERE ([Extent1].[ID] = [Extent2].[UserID]) AND ([Extent2].[RoleID] = @p__linq__0)
))
) AS [Project2]',N'@p__linq__0 int',@p__linq__0=1
go
进一步简化：
exec sp_executesql N' SELECT
[Extent1].[ID] AS [ID],
[Extent1].[Name] AS [Name],
[Extent1].[Email] AS [Email],
[Extent1].[Password] AS [Password]
FROM [dbo].[Users] AS [Extent1]
WHERE (N''admin'' <> [Extent1].[Name]) AND ( EXISTS (SELECT
1 AS [C1]
FROM [dbo].[RoleUsers] AS [Extent2]
WHERE ([Extent1].[ID] = [Extent2].[UserID]) AND ([Extent2].[RoleID] = @p__linq__0)
))
',N'@p__linq__0 int',@p__linq__0=1
go
进一步简化：
SELECT
[Users].[ID] AS [ID],
[Users].[Name] AS [Name],
[Users].[Email] AS [Email],
[Users].[Password] AS [Password]
FROM [dbo].[Users] AS [Users]
WHERE EXISTS (SELECT
1 AS [C1]
FROM [dbo].[RoleUsers] AS [RoleUsers]
WHERE ([Users].[ID] = [RoleUsers].[UserID]) AND ([RoleUsers].[RoleID] = 1)
)
进一步简化：
SELECT
ID,
Name,
Email,
Password
FROM Users
WHERE EXISTS (SELECT
1
FROM RoleUsers
WHERE (Users.ID = RoleUsers.UserID) AND (RoleUsers.RoleID = 1)
)
最终，我们看到了Entity Framework使用子查询和 EXISTS 关键字来完成 Any 的操作。
当然，如果是我们自己写SQL，可以使用 IN 关键字来达到相同的效果：
SELECT
ID,
Name,
Email,
Password
FROM Users
WHERE ID IN (SELECT
UserID
FROM RoleUsers
WHERE (Users.ID = RoleUsers.UserID) AND (RoleUsers.RoleID = 1)
)
也可以使用关联查询达到相同的效果：
SELECT
ID,
Name,
Email,
Password
FROM Users
INNER JOIN RoleUsers
ON (Users.ID = RoleUsers.UserID) AND (RoleUsers.RoleID = 1)
幸运的是，我么只需要一个 Any 关键字就完成了这个稍微复杂的查询。
不属于某个角色的用户列表（All的用法）
类似的，查询不属于某个角色的用户列表（用来添加用户到某个角色的UI界面中），使用Subsonic也有两种方法，我们只看下子查询的方式：
SqlQuery q = new Select().From<XUser>();
q.Where("1").IsEqualTo("1"); // 在职务名称中搜索
string searchText = ttbSearchMessage.Text.Trim();
if (!String.IsNullOrEmpty(searchText))
{
q.And(XUser.NameColumn).ContainsString(searchText);
} // 排除已经属于本角色的用户
int currentRoleId = GetQueryIntValue("id");
SqlQuery subQ = new Select(XRoleUser.UserIdColumn).From<XRoleUser>().Where(XRoleUser.RoleIdColumn).IsEqualTo(currentRoleId); q.And(XUser.IdColumn).NotIn(subQ); // 在查询添加之后，排序和分页之前获取总记录数
Grid1.RecordCount = q.GetRecordCount(); // 排列
q.OrderBys.Add(GetSortExpression(Grid1, XUser.Schema)); // 数据库分页
q.Paged(Grid1.PageIndex + 1, Grid1.PageSize);
XUserCollection items = q.ExecuteAsCollection<XUserCollection>(); Grid1.DataSource = items;
Grid1.DataBind();
使用Entity Framework，我们只需借助 All 关键字就能简单实现：
IQueryable<User> q = DB.Users; // 在职务名称中搜索
string searchText = ttbSearchMessage.Text.Trim();
if (!String.IsNullOrEmpty(searchText))
{
q = q.Where(u => u.Name.Contains(searchText));
} // 排除已经属于本角色的用户
int currentRoleId = GetQueryIntValue("id");
q = q.Where(u => u.Roles.All(r => r.ID != currentRoleId)); // 在查询添加之后，排序和分页之前获取总记录数
Grid1.RecordCount = q.Count(); // 排列和分页
q = SortAndPage<User>(q, Grid1); Grid1.DataSource = q;
Grid1.DataBind();
可以简单的理解：检索一些用户，要保证这些用户的所有角色没有一个是currentRoleId。
去除分页和排序后，生成的SQL语句为：
exec sp_executesql N'SELECT
[Extent1].[ID] AS [ID],
[Extent1].[Name] AS [Name],
[Extent1].[Email] AS [Email],
[Extent1].[Password] AS [Password],
[Extent1].[Enabled] AS [Enabled],
[Extent1].[Gender] AS [Gender],
[Extent1].[ChineseName] AS [ChineseName],
[Extent1].[EnglishName] AS [EnglishName],
[Extent1].[Photo] AS [Photo],
[Extent1].[QQ] AS [QQ],
[Extent1].[CompanyEmail] AS [CompanyEmail],
[Extent1].[OfficePhone] AS [OfficePhone],
[Extent1].[OfficePhoneExt] AS [OfficePhoneExt],
[Extent1].[HomePhone] AS [HomePhone],
[Extent1].[CellPhone] AS [CellPhone],
[Extent1].[Address] AS [Address],
[Extent1].[Remark] AS [Remark],
[Extent1].[IdentityCard] AS [IdentityCard],
[Extent1].[Birthday] AS [Birthday],
[Extent1].[TakeOfficeTime] AS [TakeOfficeTime],
[Extent1].[LastLoginTime] AS [LastLoginTime],
[Extent1].[CreateTime] AS [CreateTime],
[Extent1].[DeptID] AS [DeptID]
FROM [dbo].[Users] AS [Extent1]
WHERE NOT EXISTS (SELECT
1 AS [C1]
FROM [dbo].[RoleUsers] AS [Extent2]
WHERE ([Extent1].[ID] = [Extent2].[UserID]) AND (([Extent2].[RoleID] = @p__linq__0) OR (CASE WHEN ([Extent2].[RoleID] <> @p__linq__0) THEN cast(1 as bit) WHEN ([Extent2].[RoleID] = @p__linq__0) THEN cast(0 as bit) END IS NULL))
)',N'@p__linq__0 int',@p__linq__0=1
go
最终简化为：
SELECT
ID,
Name,
Email,
Password
FROM Users
WHERE NOT EXISTS (SELECT
1
FROM RoleUsers
WHERE (ID = RoleUsers.UserID) AND ((RoleUsers.RoleID = 1) OR (CASE WHEN (RoleUsers.RoleID <> 1) THEN cast(1 as bit) WHEN (RoleUsers.RoleID = 1) THEN cast(0 as bit) END IS NULL))
)
按照我的理解，其中：
CASE WHEN (RoleUsers.RoleID <> 1) THEN cast(1 as bit) WHEN (RoleUsers.RoleID = 1) THEN cast(0 as bit) END IS NULL
类似于下面的判断：
RoleUsers.RoleID IS NULL
只是不知道为啥会生成这么令人费解的代码。因为如果 RoleUsers.RoleID为NULL的话，既不会走进第一个WHEN，也不会走进第二个WHEN，自然就是NULL IS NULL为true了。
下面简单写个SELECT来验证我的想法：
select CASE WHEN (null <> 1)
THEN cast(1 as bit)
WHEN (null = 1)
THEN cast(0 as bit)
END
注意，这个NULL<>1的结果是FALSE，NULL=1的结果也是FALSE，所以最终的结果才是NULL。
再来看一个简单的SELECT查询：
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