how to convert a sql query into linq LEFT OUTER JOIN - sql

Question

This is the SQL query that returns the data I need:
SELECT
E.DESCS AS EMP, C.USERNAME,
(SELECT A.DESCS
FROM CAD_COLABORADOR H, CAD_DEPT A
WHERE H.DEPT = A.ID AND H.ID = C.ID) AS DEPT,
D.IDENTIFICADOR, D.MODELO, O.DESCS AS OFFICE,
D.K_OFFICE AS 'KEY OFFICE', S.DESCS AS SO, D.K_SO AS 'KEY SO'
FROM
IN_DESKTOP D
LEFT OUTER JOIN
CAD_COLABORADOR C ON D.ID = C.DESKTOP
INNER JOIN
CAD_EMP E ON D.EMP = E.ID
INNER JOIN
CAD_OFFICE O ON D.V_OFFICE = O.ID
INNER JOIN
CAD_SO S ON D.V_SO = S.ID ;
This is the linq expression I'm using plus has some inconsistencies since it returns the most data are not exactly the same as the SQL query:
var result = from desk in db.IN_DESKTOP
join co in db.CAD_COLABORADOR on desk.id equals co.id into egroup
from co in egroup.DefaultIfEmpty()
join e in db.CAD_EMP on desk.emp equals e.id
join o in db.CAD_OFFICE on desk.v_office equals o.id
join s in db.CAD_SO on desk.v_so equals s.id
select new
{
Empresa = e.descs,
UserName = co.username,
Departamento = co.CAD_DEPT.descs,
Identificador = desk.identificador,
Modelo = desk.modelo ,
Offices = o.descs,
KeyOfice = desk.k_office,
KeySo = desk.k_so
};

Answer 1

A left outer join in C# is just a GroupJoin followed by a SelectMany with default if empty - I've been using this extension for lambda expressions
public static class LinqExtension
{
public static IEnumerable<TResult> LeftOuterJoin<TLeft, TRight, TKey, TResult>(
this IEnumerable<TLeft> leftCollection, IEnumerable<TRight> rightCollection,
Func<TLeft, TKey> leftKey, Func<TRight, TKey> rightKey,
Func<TLeft, TRight, TResult> result)
{
return leftCollection.GroupJoin(rightCollection,
leftKey,
rightKey,
(leftObject, rightObject) => new { leftObject, rightObject })
.SelectMany(x => x.rightObject.DefaultIfEmpty(),
(l, r) => new { left = l.leftObject, right = r })
.Select(x => result.Invoke(x.left, x.right));
}
}