[Solved]-Linq Join across three tables-LINQ,C#

(from a in activities
join ov in organizationvolunteers on a.organizationid equals ov.organizationid
join av in activityvolunteers
on a.activityid equals av.volunteerid into joinedactvol
from av in joinedactvol.defaultifempty()
where ov.volunteerid==1
select new 
    {
        a.activityid,
        a.activityname,
        av.activityrole,
        a.organizationid,
        organizationname = (from o in organizations where o.organizationid == a.organizationid select o.organizationname).firstordefault()
    }).union
    (from a in activities
join av in activityvolunteers on a.activityid equals av.activityid 
where av.volunteerid==1 && a.organizationid == null
select new 
    {
        a.activityid,
        a.activityname,
        av.activityrole,
        a.organizationid,
        organizationname = ""
    })