比如@NET3的解决方案。使用shift而不是除法来测试字节的范围，因为除法占用更多的CPU成本。

private static readonly string[] UNITS = new string[] { "B", "KB", "MB", "GB", "TB", "PB", "EB" };

public static string FormatSize(ulong bytes)
{
    int c = 0;
    for (c = 0; c < UNITS.Length; c++)
    {
        ulong m = (ulong)1 << ((c + 1) * 10);
        if (bytes < m)
            break;
    }

    double n = bytes / (double)((ulong)1 << (c * 10));
    return string.Format("{0:0.##} {1}", n, UNITS[c]);
}

这个问题很老了，但是一个非常快速的c#函数可以是:

public static string PrettyPrintBytes(long numBytes)
{
    if (numBytes < 1024)
        return $"{numBytes} B";
            
    if (numBytes < 1048576)
        return $"{numBytes / 1024d:0.##} KB";

    if (numBytes < 1073741824)
        return $"{numBytes / 1048576d:0.##} MB";

    if (numBytes < 1099511627776)
        return $"{numBytes / 1073741824d:0.##} GB";

    if (numBytes < 1125899906842624)
        return $"{numBytes / 1099511627776d:0.##} TB";
            
    if (numBytes < 1152921504606846976)
        return $"{numBytes / 1125899906842624d:0.##} PB";

    return $"{numBytes / 1152921504606846976d:0.##} EB";
}

每次调用只有一次强制转换和一次除法，最多只能进行6次比较。在进行基准测试时，我发现字符串插值比使用string . format()快得多。

有一个开源项目可以做到这一点，甚至更多。

7.Bits().ToString();         // 7 b
8.Bits().ToString();         // 1 B
(.5).Kilobytes().Humanize();   // 512 B
(1000).Kilobytes().ToString(); // 1000 KB
(1024).Kilobytes().Humanize(); // 1 MB
(.5).Gigabytes().Humanize();   // 512 MB
(1024).Gigabytes().ToString(); // 1 TB

http://humanizr.net/#bytesize

https://github.com/MehdiK/Humanizer

所有溶液的混合:-)

    /// <summary>
    /// Converts a numeric value into a string that represents the number expressed as a size value in bytes,
    /// kilobytes, megabytes, or gigabytes, depending on the size.
    /// </summary>
    /// <param name="fileSize">The numeric value to be converted.</param>
    /// <returns>The converted string.</returns>
    public static string FormatByteSize(double fileSize)
    {
        FileSizeUnit unit = FileSizeUnit.B;
        while (fileSize >= 1024 && unit < FileSizeUnit.YB)
        {
            fileSize = fileSize / 1024;
            unit++;
        }
        return string.Format("{0:0.##} {1}", fileSize, unit);
    }

    /// <summary>
    /// Converts a numeric value into a string that represents the number expressed as a size value in bytes,
    /// kilobytes, megabytes, or gigabytes, depending on the size.
    /// </summary>
    /// <param name="fileInfo"></param>
    /// <returns>The converted string.</returns>
    public static string FormatByteSize(FileInfo fileInfo)
    {
        return FormatByteSize(fileInfo.Length);
    }
}

public enum FileSizeUnit : byte
{
    B,
    KB,
    MB,
    GB,
    TB,
    PB,
    EB,
    ZB,
    YB
}

我猜你要找的是“1.4 MB”而不是“1468006字节”?

我不认为在。net中有内置的方法来做到这一点。你只需要找出哪个单元是合适的，然后格式化它。

编辑:这里有一些示例代码来做到这一点:

http://www.codeproject.com/KB/cpp/formatsize.aspx

这可能不是最有效或最优化的方法，但如果您不熟悉对数数学，它更容易阅读，并且对于大多数情况来说应该足够快。

string[] sizes = { "B", "KB", "MB", "GB", "TB" };
double len = new FileInfo(filename).Length;
int order = 0;
while (len >= 1024 && order < sizes.Length - 1) {
    order++;
    len = len/1024;
}

// Adjust the format string to your preferences. For example "{0:0.#}{1}" would
// show a single decimal place, and no space.
string result = String.Format("{0:0.##} {1}", len, sizes[order]);