How can i use select to string in linq?

Answer 1

query.Single()   

That's it.

Answer 2

id = (from m in stock.StockTools
                      from ss in stock.RefStockStatus
                      where (m.statusid == 3 || m.statusid == 5) &&
                      ss.id == m.statusid && m.id == ItemID
                      select m.id).FirstOrDefault();

Answer 3

if you want to retrieve a single result user FirstOrDefault() or First().

If you use First() and the result is null.It will throws exception but not in FirstOrDefault().

var query = (from m in stock.StockTools
                      from ss in stock.RefStockStatus
                      where (m.statusid == 3 || m.statusid == 5) &&
                      ss.id == m.statusid && m.id == ItemID
                      select m.id).FirstOrDefault();

Answer 4

Just for variety...

query.Take(1)