formats a number as filesize with GB, MB, KB or bytes

filesize.cs

public class FileSize
{
    public static string FormatBytes(string bytes, int scale = 1024)
    {
        long bytesNumber = Convert.ToInt64(bytes);

        return FormatBytes(bytesNumber, scale);
    }

    public static string FormatBytes(long bytes, int scale = 1024)
    {
        string[] orders = new string[] { "GB", "MB", "KB", "Bytes" };
        long max = (long)Math.Pow(scale, orders.Length - 1);

        foreach (string order in orders)
        {
            if (bytes > max)
            {
                return String.Format("{0:##.##} {1}", Decimal.Divide(bytes, max), order);
            }

            max /= scale;
        }
        return "0 Bytes";
    }
}