using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Text.Regularexpression_rs;

namespace Hooogle

{

    public static class ExcelConvert

    {

        #region - 由数字转换为Excel中的列字母 -

        public static int ToIndex(string columnName)

        {

            if (!Regex.IsMatch(columnName.ToUpper(), @"[A-Z]+")) { throw new Exception("invalid parameter"); }

            int index = 0;

            char[] chars = columnName.ToUpper().ToCharArray();

            for (int i = 0; i < chars.Length; i++)

            {

                index += ((int)chars[i] - (int)'A' + 1) * (int)Math.Pow(26, chars.Length - i - 1);

            }

            return index - 1;

        }

        public static string ToName(int index)

        {

            if (index < 0) { throw new Exception("invalid parameter"); }

            List<string> chars = new List<string>();

            do

            {

                if (chars.Count > 0) index--;

                chars.Insert(0, ((char)(index % 26 + (int)'A')).ToString());

                index = (int)((index - index % 26) / 26);

            } while (index > 0);

            return String.Join(string.Empty, chars.ToArray());

        }

        #endregion

    }

}