System.Text.RegularExpressions.RegexCharClass.ConvertOldStringsToClass C# (CSharp) Method

        internal static string ConvertOldStringsToClass(string set, string category) {
            StringBuilder sb = new StringBuilder(set.Length + category.Length + 3);

            if (set.Length >= 2 && set[0] =='\0' && set[1] == '\0') {
                sb.Append((char) 0x1);
                sb.Append((char) (set.Length - 2));
                sb.Append((char) category.Length);
                sb.Append(set.Substring(2));
            }
            else {
                sb.Append((char) 0x0);
                sb.Append((char) set.Length);
                sb.Append((char) category.Length);
                sb.Append(set);
            }
            sb.Append(category);
            
            return sb.ToString();
        }
        

        protected static bool CharInSet(char ch, String set, String category)
        {
            string charClass = RegexCharClass.ConvertOldStringsToClass(set, category);

            return(RegexCharClass.CharInClass(ch, charClass));
        }