linq with right and left join - sql

Question

We are incorporating entity framework in my application. I have converted lot of simple stored procedures into linq queries but this one is giving me trouble and I am not sure where I am going wrong. My brain has turned into jelly and I cannot make it work. I will really appreciate your help so please bear with me.
My SQL is:
SELECT ...
FROM tblProjectAssignment
INNER JOIN tblProjectAssignmentCollection
ON tblProjectAssignment.AssignmentID = tblProjectAssignmentCollection.AssignmentID
RIGHT OUTER JOIN tblCEQRPhaseIIUsers
ON tblProjectAssignment.UserID = tblCEQRPhaseIIUsers.UserID
LEFT OUTER JOIN tblCEQRAccessUserRole
ON tblCEQRPhaseIIUsers.UserRoleTypeID = tblCEQRAccessUserRole.UserRoleTypeID
I need help converting the above to a linq query. I know DefaultIfEmpty() is used for outer joins, but the results that I get when I run the query are incorrect. So, what I need is tblCEQRPhaseIIUsers to get all results independent of the corresponding results in other table. The below query is behaving as all tables has inner joins.
var query = from PATable in db.tblProjectAssignments
from PACTable in db.tblProjectAssignmentCollections.Where(la => la.AssignmentID == PATable.AssignmentID)
from UserTable in db.tblCEQRPhaseIIUsers.Where(la => la.UserID == PATable.UserID).DefaultIfEmpty()
from UserRoleTable in db.tblCEQRAccessUserRoles.Where(la => la.UserRoleTypeID == UserTable.UserRoleTypeID).DefaultIfEmpty()
where (UserTable.FirstName.ToLower().Contains(search.FirstName.Trim().ToLower()) || search.FirstName == null)
where (UserTable.LastName.ToLower().Contains(search.LastName.Trim().ToLower()) || search.LastName == null)
where (PACTable.CEQRNumber.ToLower().Contains(search.CEQRNumber.Trim().ToLower()) || search.CEQRNumber == null)
where (PACTable.ProjectName.ToLower().Contains(search.ProjectName.Trim().ToLower()) || search.ProjectName == null)
where (PATable.IsActive == true)
where (UserTable.IsActive == true)
select new
{
AssignmentID = PATable.AssignmentID,
UserID = PATable.UserID,
FirstName = UserTable.FirstName,
MiddleName = UserTable.MiddleName ?? string.Empty,
LastName = UserTable.LastName,
UserRole = UserRoleTable.UserRoleName,
CEQRNumber = PACTable.CEQRNumber,
ProjectName = PACTable.ProjectName,
CollectionID = PACTable.CollectionID,
EmailAddress = UserTable.EmailAddress,
AssignmentIsActive = PACTable.IsActive
};

Answer 1

The problem is you can't do right joins in linq. The good news is you can rewrite your query to avoid using the right join. You do this by rearranging the tables and using left joins instead.
Currently you are doing this:
select ...
from [MainTable] m
inner join [InnerTable] i on m.Num = i.Num
right join [RightTable] r on m.Num = r.Num
left join [LeftTable] l on r.Num = l.Num
That should be equivalent to this:
select...
from [RightTable] r
left join [LeftTable] l on r.Num = l.Num
left join [MainTable] m on m.Num = r.Num
left join [InnerTable] i on m.Num = i.Num
Now you have a query without right joins, you should be able to write the linq query