multiple JOIN + SUM() query in LINQ -> can't loop in view - linq

Question

I'm trying to translate an SQL query into LINQ, but after numerous attempts, I'm still not there... Can anyone help ?
This is my working SQL statement
SELECT Users.email, SUM(Skills.level) AS SkillLevel
FROM Skills INNER JOIN
SkillsPerUser ON Skills.pk_skill_id = SkillsPerUser.fk_skill_id INNER JOIN
Users ON SkillsPerUser.fk_user_id = Users.pk_userid
GROUP BY Users.email
ORDER BY SkillLevel DESC
This is what I came up with so far, but it lacks a sum() where I hard coded the number 3, that should be the sum of Skills.level:
var allSkillsPerUser = from u in dc.Users
join spu in dc.SkillsPerUsers on u.pk_userid equals spu.fk_user_id
join s in dc.Skills on spu.fk_skill_id equals s.pk_skill_id
select new { Email = u.email, Level = s.level } into su
group su by su.Email into gsu
select new { Email = gsu.Key, SkillLevel = gsu.Sum(su => su.Level) };
ViewBag.spu = allSkillsPerUser.ToList();
The view bag gives the following error (Email can't be found, while in the variables below you can see that they do exist...):

Answer 1

context.Skills
.Join(context.SkillsPerUser, s => s.pk_skill_id, spu => spu.fk_skill_id, (s, spu) => new { Skill = s, SkillToUser = spu })
.Join(context.Users, sspu => sspu.SkillToUser.fk_userId, u => u.pk_userid, (sspu, u) => new { Email = u.Email, SkillLevel = sspu.Skill.level })
.GroupBy(su => su.Email)
.Select(g => new { Email = g.Key, SkillLevel= g.Sum(su => su.Level) })
.OrderByDescending(g => g.SkillLevel)
It's a bit simpler if you have navigation properties set up on your entities:
context.SkillsPerUser
.Select(spu => new { Email = spu.User.email, Level = spu.Skill.level }) // guessing at the navigation property names here
.GroupBy(su => su.Email)
.Select(g => new { Email = g.Key, SkillLevel = g.Sum(su => su.Level) })
.OrderByDescending(g => g.SkillLevel)
Or, using the query syntax
from u in dc.Users
join spu in dc.SkillsPerUsers on u.pk_userid equals spu.fk_user_id
join s in dc.Skills on spu.fk_skill_id equals s.pk_skill_id
select new { Email = u.email, Level = s.level } into su
group su by su.Email into gsu
select new { Email = gsu.Key, SkillLevel = gsu.Sum(su => su.Level) }
To order by the sum you can do this:
from u in dc.Users
join spu in dc.SkillsPerUsers on u.pk_userid equals spu.fk_user_id
join s in dc.Skills on spu.fk_skill_id equals s.pk_skill_id
select new { Email = u.email, Level = s.level } into su
group su by su.Email into gsu
select new { Email = gsu.Key, SkillLevel = gsu.Sum(su => su.Level) } into userSkills
orderby userSkills.SkillLevel descending