C# LINQ查询表达式中的子查询

下面是我的sql查询：

select e.id, m.id, e.Name, (select 1 where e.Id Is Null) as NotExists
    from    Employee e 
            INNER JOIN Department d
            ON e.Id = d.Id  
            LEFT JOIN Manager m
            ON e.Id = m.Id
            order by e.Name

我试图将上述查询写入LINQ，如下所示：

var result = from e in employeeRep
             join d in departmentRep
             on e.Id equals d.Id
             join m in manager
             on e.Id = m.Id
             order by e.Name
             select new
             {
               Name = e.Name,
               EmpId = e.Id,
               ManagerId = m.Id,
               DepartmentId = d.Id,
               DeparmentName = d.Name,
               NotExists = // here I want to write this query (select 1 where e.Id Is Null) as NotExists
             } ;

有人能告诉我如何做到这一点吗

谢谢

如果Id可为空，则可以执行以下操作：

select new
             {
               Name = e.Name,
               EmpId = e.Id,
               ManagerId = m.Id,
               DepartmentId = d.Id,
               DeparmentName = d.Name,
               NotExists = e.Id == null ? 1 : 0 

            }

您可以使用let关键字。它允许您创建子查询，为它们指定名称，然后在以后的代码中使用它们。虽然，它在更复杂的子查询中更有用，但在这里它也可以工作

var result = from e in employeeRep
         join d in departmentRep
         on e.Id equals d.Id
         join m in manager
         on e.Id = m.Id
         order by e.Name
         let mySub = // write your query here.
         select new
         {
           Name = e.Name,
           EmpId = e.Id,
           ManagerId = m.Id,
           DepartmentId = d.Id,
           DeparmentName = d.Name,
           NotExists = mySub
         };

---

我不确定这一点，因为我从来没有尝试过，我一定会尝试，看看它是否解决了我的问题。无论如何，我承认，如果你只想在ID为null时分配一个数字，那么这个解决方案有点过分了。我添加它是为了防止您或其他人希望在LINQ查询中检索更复杂的内容。不过，它也可以应用于您的问题。谢谢您的回复