获取汉字拼音首字母[C#]

static public string getSpells(string input)
        {
int len = input.Length;
            string reVal = "";
            for(int i=0;i<len;i++)
            {
                reVal += getSpell(input.Substring(i,1));
            }
            return reVal;
        }

        static public string getSpell(string cn)
        {
            byte[] arrCN = Encoding.Default.GetBytes(cn);
            if(arrCN.Length > 1)
            {
                int area = (short)arrCN[0];
                int pos = (short)arrCN[1];
                int code = (area<<8) + pos;
                int[] areacode = {45217,45253,45761,46318,46826,47010,47297,47614,48119,48119,49062,49324,49896,50371,50614,50622,50906,51387,51446,52218,52698,52698,52698,52980,53689,54481};
                for(int i=0;i<26;i++)
                {
                    int max = 55290;
                    if(i != 25) max = areacode[i+1];
                    if(areacode[i]<=code && code<max)
                    {
                        return Encoding.Default.GetString(new byte[]{(byte)(65+i)});
                    }
                }
                return "?";
            }
            else return cn;
        }