{C#·文件大小格式转换}

最新推荐文章于 2020-06-12 17:50:44 发布

转载最新推荐文章于 2020-06-12 17:50:44 发布 · 1.9k 阅读

文章标签：

#c# #string #object #null #file #class

本文介绍了一种在C#中实现文件大小格式化的实用方法，包括自定义格式提供程序(FileSizeFormatProvider)的使用，以及通过扩展方法和Windows API进行文件大小格式化的替代方案。

转自Stackoverflow：http://stackoverflow.com/questions/128618/c-file-size-format-provider

public class FileSizeFormatProvider : IFormatProvider, ICustomFormatter 
{ 
    public object GetFormat(Type formatType) 
    { 
        if (formatType == typeof(ICustomFormatter)) return this; 
        return null; 
    } 
 
    private const string fileSizeFormat = "fs"; 
    private const Decimal OneKiloByte = 1024M; 
    private const Decimal OneMegaByte = OneKiloByte * 1024M; 
    private const Decimal OneGigaByte = OneMegaByte * 1024M; 
 
    public string Format(string format, object arg, IFormatProvider formatProvider) 
    {     
        if (format == null || !format.StartsWith(fileSizeFormat))     
        {     
            return defaultFormat(format, arg, formatProvider);     
        } 
 
        if (arg is string)     
        {     
            return defaultFormat(format, arg, formatProvider);     
        } 
 
        Decimal size; 
 
        try     
        {     
            size = Convert.ToDecimal(arg);     
        }     
        catch (InvalidCastException)     
        {     
            return defaultFormat(format, arg, formatProvider);     
        } 
 
        string suffix; 
        if (size > OneGigaByte) 
        { 
            size /= OneGigaByte; 
            suffix = "GB"; 
        } 
        else if (size > OneMegaByte) 
        { 
            size /= OneMegaByte; 
            suffix = "MB"; 
        } 
        else if (size > OneKiloByte) 
        { 
            size /= OneKiloByte; 
            suffix = "kB"; 
        } 
        else 
        { 
            suffix = " B"; 
        } 
 
        string precision = format.Substring(2); 
        if (String.IsNullOrEmpty(precision)) precision = "2"; 
        return String.Format("{0:N" + precision + "}{1}", size, suffix); 
 
    } 
 
    private static string defaultFormat(string format, object arg, IFormatProvider formatProvider) 
    { 
        IFormattable formattableArg = arg as IFormattable; 
        if (formattableArg != null) 
        { 
            return formattableArg.ToString(format, formatProvider); 
        } 
        return arg.ToString(); 
    } 
}

使用方法：

Console.WriteLine(String.Format(new FileSizeFormatProvider(), "File size: {0:fs}", 100));
Console.WriteLine(String.Format(new FileSizeFormatProvider(), "File size: {0:fs}", 10000));

public static class ExtensionMethods
{
  public static string ToFileSize(this long l)
  {
  return String.Format(new FileSizeFormatProvider(), "{0:fs}", l);
  }
}
3.

long l = 100000000;
Console.WriteLine(l.ToFileSize());

另一种比较好的方法：

[DllImport("Shlwapi.dll", CharSet = CharSet.Auto)]
public static extern long StrFormatByteSize( long fileSize, [MarshalAs(UnmanagedType.LPTStr)] StringBuilder buffer, int bufferSize );