NPOI根据列索引获取列名

public static string ConvertColumnIndexToColumnName(int index)

        {

            index = index + ;

            int system = ;

            char[] digArray = new char[];

            int i = ;

            while (index > )

            {

                int mod = index % system;

                if (mod == )

                    mod = system;

                digArray[i++] = (char)(mod -  + 'A');

                index = (index - ) / ;

            }

            StringBuilder sb = new StringBuilder(i);

            for (int j = i - ; j >= ; j--)

            {

                sb.Append(digArray[j]);

            }

            return sb.ToString();

        }