Cannot use select in LINQ query

Question

I have a method in which I'm trying to return some database results through a LINQ query, however Visual Studio is not allowing me to use a select statement. This is what I have so far:

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;
}

However, in the LINQ segment, I would like it to be as follows:

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

Is there a particular reason why I'm not being allowed to add the last select portion?

do you mean to say you are not getting the select method in intellisense? — Kundan Singh Chouhan, Mar 04 '13 at 17:11
Correct. When I try to add it manually it doesn't like it, either. — Chris V., Mar 04 '13 at 17:12

score 2 · Accepted Answer · answered Mar 04 '13 at 17:15

2

Correct your

where employee.User_Id equals userGuid

with

where employee.User_Id == userGuid

answered Mar 04 '13 at 17:15

aush

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So just to clarify, == and equals work similarly in regular c# code, meaning equals is equivalent to .Equals()? Apologies, I'm somewhat new to using LINQ. – Chris V. Mar 04 '13 at 17:16
@Chris V., *equals* is a contextual keyword which is used only in a join clause in a query expression. – aush Mar 04 '13 at 17:19
i believe that equals is used only within linq as apart of the join syntax, == and .Equals are a different mechanism, i may be incorrect though – AdamWhite Mar 04 '13 at 17:19
Ah, okay. So it's only for use in join conditions. – Chris V. Mar 04 '13 at 17:19

AdamWhite · Answer 2 · 2013-03-04T17:26:52.590

2

The issue is with your where clause:

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

Should be:

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

edited Mar 04 '13 at 17:26

answered Mar 04 '13 at 17:16

AdamWhite

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Isn't == only for use with numerical data though? I was under the impression that Guids are string data – Chris V. Mar 04 '13 at 17:17
@ChrisV. The `==` operator can be overloaded for any type. – Timothy Shields Mar 04 '13 at 17:21
@ChrisV. take a look at this [C# difference between `==` and .Equals()](http://stackoverflow.com/questions/814878/c-sharp-difference-between-and-equals) – psubsee2003 Mar 04 '13 at 17:22
@ChrisV == and .Equals can be used to compare value types and reference types. – AdamWhite Mar 04 '13 at 17:22
1

**AND**, "equals" is a LINQ keyword that is only used in the `join`. – GalacticCowboy Mar 04 '13 at 17:24

Cannot use select in LINQ query

2 Answers2