数字转成字母的方法

private static string Num_to_letter(int value)
{
//此处判断输入的是否是正整数数字
if (Regex.IsMatch(value.ToString(), "^\\d+$"))
{
int remainder = value % 26;
//remainder = (remainder == 0) ? 26 : remainder;
int front = (value - remainder) / 26;
if (front == 0)
{
return Level[remainder];
}
else if (front < 26)
{
return Level[front - 1] + Level[remainder];
}
else
{
return Num_to_letter(front) + Level[remainder];
}
}
else
{
return string.Empty;
}

}