代码

        static string GetUnitNum(double num)
        {
            string[] unit = new string[] { "B", "KB", "MB", "GB", "TB" };
            long n = 1024;
            int i = 0;
            while (num > n)
            {
                num /= n;
                i++;
            }
            return Math.Round(num, 2) + unit[i];
        }

测试结果