I have the following code below and it's taking quite some time to run due to high volume of answers there are. Is there anyway I could speed it up?

var controlStrings = answerControlStrings.Where(a => a.ControlN.Substring(a.ControlN.IndexOf('_') + 1, a.ControlN.Length - a.ControlN.IndexOf('_') - 1).Equals(newAnswer.QVar, StringComparison.InvariantCultureIgnoreCase));
            if (controlStrings.Count() > 0)
            {
                newAnswer.CatiControlStrings.Add("en", controlStrings.Where(c => c.CultureN.Contains("cati") && c.CultureN.Contains("en")).ToList());
                newAnswer.WebControlStrings.Add("en", controlStrings.Where(c => c.CultureN.Contains("web") && c.CultureN.Contains("en")).ToList());
                newAnswer.CatiControlStrings.Add("es", controlStrings.Where(c => c.CultureN.Contains("cati") && c.CultureN.Contains("es")).ToList());
                newAnswer.WebControlStrings.Add("es", controlStrings.Where(c => c.CultureN.Contains("web") && c.CultureN.Contains("es")).ToList());
            }