1-liner(加上前缀常量)

const String prefixes = " KMGTPEY";
/// <summary> Returns the human-readable file size for an arbitrary, 64-bit file size. </summary>
public static String HumanSize(UInt64 bytes)
    => Enumerable
    .Range(0, prefixes.Length)
    .Where(i => bytes < 1024U<<(i*10))
    .Select(i => $"{(bytes>>(10*i-10))/1024:0.###} {prefixes[i]}B")
    .First();

或者，如果你想减少LINQ对象的分配，使用相同的for循环变量:

/// <summary>
/// Returns the human-readable file size for an arbitrary, 64-bit file size.
/// </summary>
public static String HumanSize(UInt64 bytes)
{
    const String prefixes = " KMGTPEY";
    for (var i = 0; i < prefixes.Length; i++)
        if (bytes < 1024U<<(i*10))
            return $"{(bytes>>(10*i-10))/1024:0.###} {prefixes[i]}B";

    throw new ArgumentOutOfRangeException(nameof(bytes));
}

请求函数的测试和显著优化版本发布在这里:

c#人类可读文件大小-优化的函数

源代码:

// Returns the human-readable file size for an arbitrary, 64-bit file size 
// The default format is "0.### XB", e.g. "4.2 KB" or "1.434 GB"
public string GetBytesReadable(long i)
{
    // Get absolute value
    long absolute_i = (i < 0 ? -i : i);
    // Determine the suffix and readable value
    string suffix;
    double readable;
    if (absolute_i >= 0x1000000000000000) // Exabyte
    {
        suffix = "EB";
        readable = (i >> 50);
    }
    else if (absolute_i >= 0x4000000000000) // Petabyte
    {
        suffix = "PB";
        readable = (i >> 40);
    }
    else if (absolute_i >= 0x10000000000) // Terabyte
    {
        suffix = "TB";
        readable = (i >> 30);
    }
    else if (absolute_i >= 0x40000000) // Gigabyte
    {
        suffix = "GB";
        readable = (i >> 20);
    }
    else if (absolute_i >= 0x100000) // Megabyte
    {
        suffix = "MB";
        readable = (i >> 10);
    }
    else if (absolute_i >= 0x400) // Kilobyte
    {
        suffix = "KB";
        readable = i;
    }
    else
    {
        return i.ToString("0 B"); // Byte
    }
    // Divide by 1024 to get fractional value
    readable = (readable / 1024);
    // Return formatted number with suffix
    return readable.ToString("0.### ") + suffix;
}

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]);

1-liner(加上前缀常量)

const String prefixes = " KMGTPEY";
/// <summary> Returns the human-readable file size for an arbitrary, 64-bit file size. </summary>
public static String HumanSize(UInt64 bytes)
    => Enumerable
    .Range(0, prefixes.Length)
    .Where(i => bytes < 1024U<<(i*10))
    .Select(i => $"{(bytes>>(10*i-10))/1024:0.###} {prefixes[i]}B")
    .First();

或者，如果你想减少LINQ对象的分配，使用相同的for循环变量:

/// <summary>
/// Returns the human-readable file size for an arbitrary, 64-bit file size.
/// </summary>
public static String HumanSize(UInt64 bytes)
{
    const String prefixes = " KMGTPEY";
    for (var i = 0; i < prefixes.Length; i++)
        if (bytes < 1024U<<(i*10))
            return $"{(bytes>>(10*i-10))/1024:0.###} {prefixes[i]}B";

    throw new ArgumentOutOfRangeException(nameof(bytes));
}

string[] suffixes = { "B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB" };
int s = 0;
long size = fileInfo.Length;

while (size >= 1024)
{
    s++;
    size /= 1024;
}

string humanReadable = String.Format("{0} {1}", size, suffixes[s]);

下面是@ deepe1的BigInteger版本的答案，它绕过了long的大小限制(因此支持yottabyte和理论上的任何后面的限制):

public static string ToBytesString(this BigInteger byteCount, string format = "N3")
{
    string[] suf = { "B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "YiB" };
    if (byteCount.IsZero)
    {
        return $"{0.0.ToString(format)} {suf[0]}";
    }

    var abs = BigInteger.Abs(byteCount);
    var place = Convert.ToInt32(Math.Floor(BigInteger.Log(abs, 1024)));
    var pow = Math.Pow(1024, place);

    // since we need to do this with integer math, get the quotient and remainder
    var quotient = BigInteger.DivRem(abs, new BigInteger(pow), out var remainder);
    // convert the remainder to a ratio and add both back together as doubles
    var num = byteCount.Sign * (Math.Floor((double)quotient) + ((double)remainder / pow));

    return $"{num.ToString(format)} {suf[place]}";
}