IEnumerable<string> lines = SelectLines();
List<Item> items = lines.Select(l=>ParseToItem(l)).ToList();
var itemOfIterest = items.FirstOrDefault(IsItemOfIterest);

var itemOfIterest = lines.FirstOrDefault(l=>IsItemOfIterest(ParseToItem(l));

IEnumerable<string> SelectLines()
 {
  ...
  using(var reader = ...)
  while((line=reader.ReadLine())!=null)
   yield return line;
 }