convert sql to linq -- left join -- getting error

Question

need to convert sql to linq.

 
select p.firstname,p.lastname,a.assignmentname,asg.pointsawarded,a.pointspossible,a.duedatetime,asg.submissiondatetime
from person2 p
inner join coursesectionroster cs
on cs.personid = p.personid
inner join assignment a
on a.coursesectionid = cs.coursesectionid
left join assignmentsubmission asg
on a.assignmentid=asg.assignmentid
where cs.coursesectionid='b78a6efe-ac77-4e49-806a-fc2fad71068b'
and cs.courserole=2