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
     
       chars = new List
      
       ();    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());}
      
     

转自：https://www.cnblogs.com/lhlong/p/7920408.html