//inner join
var query = from a in data.A
join b in data.B
on a.bid equals b.id
select new
{
id=a.id,
name = b.name
};
//left join
var query = from a in data.A
join b in data.B
on a.bid equals b.id into ab
from b in ab.DefaultIfEmpty()
join c in data.C
on b.cid equals c.id into bc
from c in bc.DefaultIfEmpty()
join d in data.D
on c.did equals d.id into cd
from d in cd.DefaultIfEmpty()
join e in data.E
on d.eid equals e.id into ce
from e in ce.DefaultIfEmpty()
select new
{
Id = a.Id,
Name = b==null?"":b.Name,
Pro = c==null?"":c.Pro,
IpAdd = d==null?"":d.IpAdd
};