First Non-Repeated Character from a UNICODE String using Hash Table

the only difference here is the input string can be UNICODE (65000 characters) instead of ASCII Code (256 characters) so using a hash table makes more sense

 public static char FirstNonRepeatedHash(string stringToCheck)
        {
            Hashtable cHash = new Hashtable();
            int length = stringToCheck.Length;
            int i = 0;
            bool hashPresent = false;
            char charToReturn = '\0';

            for (i = 0; i < length; i++)
            {
                hashPresent = cHash.Contains(stringToCheck[i]);
                if (hashPresent)
                {
                    cHash[stringToCheck[i]] = 1 + Convert.ToInt32(cHash[stringToCheck[i]]);
                }
                else
                {
                    cHash.Add(Convert.ToChar(stringToCheck[i]), 1);
                }

            }
            
            for (i = 0; i < length; i++)
            {
                if (Convert.ToInt32(cHash[stringToCheck[i]]) ==1 )
                {
                    charToReturn = stringToCheck[i];
                    break;
                }
            }
            return charToReturn;
        }