Excel列字母与数字的转换

最近工作中发现需要转换Excel列名，例如A列序号为0，Z列序号为25，ZB列则为27
发现字母列名实际为26进制，于是写了如下Helper Class来解决我的问题：

1 public class ExcelColumnTranslator
2 {
3     private ExcelColumnTranslator()
4     {
5     }
6
7     public static int ToIndex(string columnName)
8     {
9         if (!Regex.IsMatch(columnName.ToUpper(), @"[A-Z]+"))
10             throw new Exception("invalid parameter");
11         int index = 0;
12         char[] chars = columnName.ToUpper().ToCharArray();
13         for (int i = 0; i < chars.Length; i++)
14         {
15             index += ((int)chars[i] - (int)'A' + 1) * (int)Math.Pow(26, chars.Length - i - 1);
16         }
17         return index - 1;
18     }
19
20     public static string ToName(int index)
21     {
22         if (index < 0)
23             throw new Exception("invalid parameter");
24         List<string> chars = new List<string>();
25         do
26         {
27             if (chars.Count > 0) index--;
28             chars.Insert(0, ((char)(index % 26 + (int)'A')).ToString());
29             index = (int)((index - index % 26) / 26);
30         } while (index > 0);
31
32         return String.Join(string.Empty, chars.ToArray());
33     }
34 }
35