entity framework - LINQ to Entities 4: Query with calculation in where clause -

i have table datetime "timestamp" column , int "timeoutseconds" column. want retrieve records table datetime.now - timestamp > timeoutseconds. in stored proc no brainer using getdate():

select * schema.tablename mp (getdate() - mp.[timestamp]) > mp.timeout 

however, entity framework using either linq syntax or lambda cannot because seems lambda input variable (mp) cannot used part of calculation part of predicate, not compile:

var records = context.tablename.where(mp => (datetime.now - mp.timestamp) > mp.timeout); 

this not compile.

i don't want retrieve whole table filtering in memory , rather not use stored proc or entity sql. options here?

this not compile because comparing (datetime.now - mp.timestamp) has return type system.timespan int. first solution comes mind do

where(mp => (datetime.now - mp.timestamp) > new timespan(0, 0, 0, mp.timeout)) 

unfortunately doesn't seem work in ef, if have ms sql server db, can use sqlfunctions in ef4:

var records = context.               tablename.               where(mp => system.data.objects.sqlclient.sqlfunctions.                           datediff("s", mp.timestamp, datetime.now) > mp.timeout); 

http://msdn.microsoft.com/en-us/library/dd487052.aspx