Question

I need to do the following thing:

var a = from c in DB.Customers 
        where (from t1 in DB.Table1 where t1.Date >= DataTime.Now 
               select t1.ID).Contains(c.ID) && 
              (from t2 in DB.Table2 where t2.Date >= DataTime.Now 
               select t2.ID).Contains(c.ID) 
        select c

It doesn’t want to run. I get the following error:

Timeout expired. The timeout period
elapsed prior to completion of the
operation or the server is not
responding.

But when I try to run:

var a = from c in DB.Customers 
        where (from t1 in DB.Table1 where t1.Date >= DataTime.Now 
               select t1.ID).Contains(c.ID)
        select c

Or:

var a = from c in DB.Customers 
        where (from t2 in DB.Table2 where t2.Date >= DataTime.Now 
               select t2.ID).Contains(c.ID) 
        select c

It works! I’m sure that there both IN queries contain some customers ids.

Answer 1

In case this is an efficiency issue, it would be a good idea to look at the SQL query that LINQ to SQL produces (in debug mode, place the mouse cursor over a). In any case, you could try rewriting the query using join. Something like this should do the trick:

var a = from c in DB.Customers  
        join t1 in DB.Table1 on c.ID equals t1.ID
        join t2 in DB.Table2 on c.ID equals t2.ID
        where t1.Date >= DateTimeNow && t2.Date >= DateTimeNow 
        select c