I would use for or foreach when iterating over a whole record set. Like Jose’s first foreach. Then when grabbing only one record I would use a linq statement like FirstOrDefault.
Jose, would making the linq query like,
var serial = Db.SerialNo.FirstOrDefault(s=> s.Company == x.Company && s.SerialNumber == x.SerialNumber && x.PartNum == s.PartNum)
be more efficient?