Question

我有一个方法，我试图通过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。这就是我到目前为止所做的：

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;
}

但是，在LINQ细分中，我喜欢它如下：

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

是否有一个特殊原因导致我无法添加最后一个选择部分？

Answer 1

纠正你的

where employee.User_Id equals userGuid

带

where employee.User_Id == userGuid

Answer 2

问题在于你的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

无法在LINQ查询中使用select

2 个答案: