这是一种相当简洁的方法：

static readonly string[] SizeSuffixes = 
                   { "bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };
static string SizeSuffix(Int64 value, int decimalPlaces = 1)
{
    if (decimalPlaces < 0) { throw new ArgumentOutOfRangeException("decimalPlaces"); }
    if (value < 0) { return "-" + SizeSuffix(-value); } 
    if (value == 0) { return string.Format("{0:n" + decimalPlaces + "} bytes", 0); }

    // mag is 0 for bytes, 1 for KB, 2, for MB, etc.
    int mag = (int)Math.Log(value, 1024);

    // 1L << (mag * 10) == 2 ^ (10 * mag) 
    // [i.e. the number of bytes in the unit corresponding to mag]
    decimal adjustedSize = (decimal)value / (1L << (mag * 10));

    // make adjustment when the value is large enough that
    // it would round up to 1000 or more
    if (Math.Round(adjustedSize, decimalPlaces) >= 1000)
    {
        mag += 1;
        adjustedSize /= 1024;
    }

    return string.Format("{0:n" + decimalPlaces + "} {1}", 
        adjustedSize, 
        SizeSuffixes[mag]);
}

这是我建议的原始实现，可能会稍慢一些，但易于遵循：

static readonly string[] SizeSuffixes = 
                  { "bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };

static string SizeSuffix(Int64 value, int decimalPlaces = 1)
{
    if (value < 0) { return "-" + SizeSuffix(-value); }

    int i = 0;
    decimal dValue = (decimal)value;
    while (Math.Round(dValue, decimalPlaces) >= 1000)
    {
        dValue /= 1024;
        i++;
    }

    return string.Format("{0:n" + decimalPlaces + "} {1}", dValue, SizeSuffixes[i]);
}

Console.WriteLine(SizeSuffix(100005000L));