.net - Expression Trees and Joins -

expression<func<account, ienumerable<attachment>>> attachments =  t => attachmentbuilder.populate("companyname", t.accountid.tostring());   var q = cxt.accounts.select(e => new  {     accountid = e.accountid,         description = e.accountdescription,  }); 

what ideally want join attachments expression (results) q (accounts- ienumerable) can filter accountid dynamically passed ui "t.accountid.tostring()" dont want use sub query have loads of attachments looking more join type solution dynamic linq , expression trees passing account id dynamically. thanks,