c# - Linq 2 SQL Convert to Outer Join -

i have linq sql query features several joins. want convert 1 of them outer join. problem query has clause. how can convert query use left join on ordercertification table instead of inner join?

the following query did not work (caused app crash):

var ordersummaries = os in dborder.queryordersummaries().where(os => orders.contains(os.orderid))    join o in dc.orders on os.orderid equals o.orderid    join oa in dc.orderaddresses on os.orderid equals oa.orderid    join d in dc.vdoctors on o.doctorid equals d.doctorid    join c in dc.ordercertifications on os.orderid equals c.orderid oc    certification in oc.defaultifempty()    select new batchorderitem {       ordersummary = os,       order = o,       shipto = oa,       prescriber = d,       certificationcontact = certification     }; 

the trick using defaultifempty return rows first table. check out example: http://msdn.microsoft.com/en-us/library/bb397895.aspx