Question

我有以下Transact-Sql，我试图转换为LINQ ...并挣扎。

SELECT * FROM Project
WHERE Project.ProjectId IN (SELECT ProjectId FROM ProjectMember Where MemberId = 'a45bd16d-9be0-421b-b5bf-143d334c8155')

非常感谢任何帮助......如果可能的话，我想用Lambda表达式来做。

提前致谢！

Answer 1

GFrizzle打败了我。但这是一个C＃版本

var projectsMemberWorkedOn = from p in Projects
                    join projectMember in ProjectMembers on
                        p.ProjectId equals projectMember.ProjectId
                    where projectMember.MemberId == "a45bd16d-9be0-421b-b5bf-143d334c8155"
                    select p;

作为一个纯粹的LINQ方法链版本的奖励：

var projectsMemberWorkedOn =
            Projects.Join( ProjectMembers, p => p.ProjectId, projectMember => projectMember.ProjectId,
                ( p, projectMember ) => new { p, projectMember } )
                .Where( @t => @t.projectMember.MemberId == "a45bd16d-9be0-421b-b5bf-143d334c8155" )
                .Select(@t => @t.p );

Answer 2

在这种情况下，您可以使用.Contains（），如下所示：

var projects = 
from p in db.Projects
where db.ProjectMembers.Where(m => m.MemberId == "a45bd16d-9be0-421b-b5bf-143d334c8155").Select(pp => pp.ProjectID).Contains(p.ProjectID)
select p;

Answer 3

不需要lambda，你只需要一个简单的LINQ连接：

From p in db.Projects _
Join m in db.ProjectMember On p.ProjectId Equals m.ProjectId _
Where m.MemberId = "a45bd16d-9be0-421b-b5bf-143d334c8155" _
Select p

Answer 4

您可能需要 Any（）运算符：

var q = db.Projects
          .Where(p => db.ProjectMembers
                        .Where(pm => pm.MemberId == memberId)
                        .Any  (pm => p.ProjectId == pm.ProjectId));

由于db.ProjectMembers.Where(...)的结果集始终相同，因此您可以将其拆分以便只执行一次：

var projectMembers = db.ProjectMembers.Where(pm => pm.MemberId == memberId);
var q              = db.Projects
                       .Where(p  => projectMembers
                                    .Any(pm => p.ProjectId == pm.ProjectId));

如何使用LAMBDA表达式在LINQ中执行IN或CONTAINS？

4 个答案: