不能在LINQ查询中使用select

Question

我有一种方法，我尝试通过LINQ查询返回一些数据库结果，但是Visual Studio不允许我使用select语句。这是我到目前为止有：

public static int GetCurrentUserDepartmentId(Guid userGuid) 
{ 
    int departmentId = -1; 

    using (PTMS_DataEntities entities = new PTMS_DataEntities()) 
    { 
     var userDepartment = from employee in entities.Employees 
          join user in entities.aspnet_Users 
          on employee.User_Id equals user.UserId 
          where employee.User_Id equals userGuid          

     departmentId = (int)userDepartment;     
    } 

    return departmentId; 
} 

然而，在LINQ段，我会像它到如下：

from employee in entities.Employees 
join user in entities.aspnet_Users 
on employee.User_Id equals user.UserId 
where employee.User_Id equals userGuid 
select employee.Department_Id 

有，为什么我不是一个特别的原因被允许添加最后的选择部分？

Answer 1

纠正你

where employee.User_Id equals userGuid 

与

where employee.User_Id == userGuid 

Answer 2

的问题是与您的where子句：

var userDepartment = from employee in entities.Employees 
         join user in entities.aspnet_Users 
         on employee.User_Id equals user.UserId 
         where employee.User_Id equals userGuid 

应该是：

var userDepartment = from employee in entities.Employees 
         join user in entities.aspnet_Users 
         on employee.User_Id equals user.UserId 
         where employee.User_Id == userGuid 
         select employee.Department_Id