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]);

这里没有什么东西完全符合我的需要，我根据这个线程制作了我自己的，所以这里是我的长扩展，允许您根据标准选择格式要求。

绝对不是最快的，但很灵活。支持EB/EiB。

// <summary>
/// <paramref name="byteCount"/> The original size in bytes ( 8 bits )
/// <paramref name="notationFormat"/> is supported in the following ways:
/// [    'B' / 'b' : Binary :   Kilobyte (KB) is 1024 bytes, Megabyte (MB) is 1048576 bytes, etc    ]
/// [    'I' / 'i' : IEC:       Kibibyte (KiB) is 1024 bytes, Mebibyte (MiB) is 1048576 bytes, etc    ]
/// [    'D' / 'd' : Decimal :  Kilobyte (KB) is 1000 bytes, Megabyte (MB) is 1000000 bytes, etc    ]
/// </summary>

public static string ToDataSizeString( this long byteCount, char notationFormat = 'b' )
{
    char[] supportedFormatChars = { 'b', 'i', 'd' };

    var lowerCaseNotationFormat = char.ToLowerInvariant( notationFormat );

    // Stop shooting holes in my ship!
    if ( !supportedFormatChars.Contains( lowerCaseNotationFormat ) )
    {
        throw new ArgumentException( $"notationFormat argument '{notationFormat}' not supported" );
    }

    long ebLimit = 1152921504606846976;
    long pbLimit = 1125899906842624;
    long tbLimit = 1099511627776;
    long gbLimit = 1073741824;
    long mbLimit = 1048576;
    long kbLimit = 1024;

    var ebSuffix = "EB";
    var pbSuffix = "PB";
    var tbSuffix = "TB";
    var gbSuffix = "GB";
    var mbSuffix = "MB";
    var kbSuffix = "KB";
    var bSuffix  = " B";

    switch ( lowerCaseNotationFormat )
    {
        case 'b':
            // Sweet as
            break;

        case 'i':
            // Limits stay the same, suffixes need changed
            ebSuffix = "EiB";
            pbSuffix = "PiB";
            tbSuffix = "TiB";
            gbSuffix = "GiB";
            mbSuffix = "MiB";
            kbSuffix = "KiB";
            bSuffix  = "  B";
            break;

        case 'd':
            // Suffixes stay the same, limits need changed
            ebLimit = 1000000000000000000;
            pbLimit = 1000000000000000;
            tbLimit = 1000000000000;
            gbLimit = 1000000000;
            mbLimit = 1000000;
            kbLimit = 1000;
            break;

        default:
            // Should have already Excepted, but hey whatever
            throw new ArgumentException( $"notationFormat argument '{notationFormat}' not supported" );

    }

    string fileSizeText;

    // Exa/Exbi sized
    if ( byteCount >= ebLimit )
    {
        fileSizeText = $"{( (double)byteCount / ebLimit ):N1} {ebSuffix}";
    }
    // Peta/Pebi sized
    else if ( byteCount >= pbLimit )
    {
        fileSizeText = $"{( (double)byteCount / pbLimit ):N1} {pbSuffix}";
    }
    // Tera/Tebi sized
    else if ( byteCount >= tbLimit )
    {
        fileSizeText = $"{( (double)byteCount / tbLimit ):N1} {tbSuffix}";
    }
    // Giga/Gibi sized
    else if ( byteCount >= gbLimit )
    {
        fileSizeText = $"{( (double)byteCount / gbLimit ):N1} {gbSuffix}";
    }
    // Mega/Mibi sized
    else if ( byteCount >= mbLimit )
    {
        fileSizeText = $"{( (double)byteCount / mbLimit ):N1} {mbSuffix}";
    }
    // Kilo/Kibi sized
    else if ( byteCount >= kbLimit )
    {
        fileSizeText = $"{( (double)byteCount / kbLimit ):N1} {kbSuffix}";
    }
    // Byte sized
    else
    {
        fileSizeText = $"{byteCount} {bSuffix}";
    }

    return fileSizeText;
}

下面是一个Log10的方法:

using System;

class Program {
   static string NumberFormat(double n) {
      var n2 = (int)Math.Log10(n) / 3;
      var n3 = n / Math.Pow(1e3, n2);
      return String.Format("{0:f3}", n3) + new[]{"", " k", " M", " G"}[n2];
   }

   static void Main() {
      var s = NumberFormat(9012345678);
      Console.WriteLine(s == "9.012 G");
   }
}

https://learn.microsoft.com/dotnet/api/system.math.log10

这是我编的，效果很好。

public string[] DetermineDigitalSize(string filename)
        {
            string[] result = new string[2];
            string[] sizes = { "B", "KB", "MB", "GB", "GB" };
            double len = new FileInfo(filename).Length;
             double adjustedSize = len;
            double testSize = 0;
            int order = 0;
            while (order< sizes.Length-1)
            {
                testSize = adjustedSize / 1024;
                if (testSize >= 1) { adjustedSize = testSize; order++; }
                else { break; }
            }
            result[0] = $"{adjustedSize:f2}";
            result[1] = sizes[order];
            return result;
        }

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;
}

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