matching string in a list
var filtered = target.Where(str => str.Contains("C"));

target.RemoveAll(str => !str.Contains("C"));

Regex validate = new Regex(".a.", RegexOptions.IgnoreCase);
 var filtered = target.Where(str => validate.Match(str).Success);

var m = from t in target
                where t[0] == 'C'
                select t;