文件大小的格式提供者 [英] File-size format provider
问题描述
有没有简单的方法来创建一个使用 IFormatProvider 的类来写出一个用户友好的文件大小?
public static string GetFileSizeString(string filePath)
{
FileInfo info = new FileInfo(@c:\windows\\\
otepad.exe);
long size = info.Length;
string sizeString = size.ToString(FileSizeFormatProvider); //这是类魔法的地方...
}
格式化为 2,5 MB , 3,9 GB , 670字节等字符串。
$ div b
$ b $ (formatType == typeof(ICustomFormatter))public class FileSizeFormatProvider:IFormatProvider,ICustomFormatter
{
public object GetFormat(Type formatType)
{
if(formatType == typeof返回这个;
返回null;
}
private const string fileSizeFormat =fs;
private const十进制OneKiloByte = 1024M;
私人常量十进制OneMegaByte = OneKiloByte * 1024M;
private const Decimal OneGigaByte = OneMegaByte * 1024M;
$ b公共字符串格式(字符串格式,对象arg,IFormatProvider formatProvider)
{
if(format == null ||!format.StartsWith(fileSizeFormat))
{
返回defaultFormat(format,arg,formatProvider);
$ b $ if(arg is string)
{
return defaultFormat(format,arg,formatProvider);
}
十进制大小;
尝试
{
size = Convert.ToDecimal(arg);
catch(InvalidCastException)
{
return defaultFormat(format,arg,formatProvider);
}
字符串后缀;
if(size> OneGigaByte)
{
size / = OneGigaByte;
后缀=GB;
}
else if(size> OneMegaByte)
{
size / = OneMegaByte;
后缀=MB;
}
else if(size> OneKiloByte)
{
size / = OneKiloByte;
后缀=kB;
}
else
{
suffix =B;
}
string precision = format.Substring(2);
if(String.IsNullOrEmpty(precision))precision =2;
return String.Format({0:N+ precision +} {1},size,suffix);
$ b 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();
$ b $ / code $ / pre
使用的一个例子是: Console.WriteLine(String.Format(new FileSizeFormatProvider(),文件大小:{0:fs}),100) );
Console.WriteLine(String.Format(new FileSizeFormatProvider(),File size:{0:fs},10000));
) 如果您使用的是C#3.0,则可以使用扩展方法来获得所需的结果: 您可以像这样使用它。 希望这有帮助。 > Is there any easy way to create a class that uses IFormatProvider that writes out a user-friendly file-size? It should result in strings formatted something like "2,5 MB", "3,9 GB", "670 bytes" and so on. I use this one, I get it from the web an example of use would be: Credits for http://flimflan.com/blog/FileSizeFormatProvider.aspx There is a problem with ToString(), it's expecting a NumberFormatInfo type that implements IFormatProvider but the NumberFormatInfo class is sealed :( If you're using C# 3.0 you can use an extension method to get the result you want: You can use it like this. Hope this helps. 这篇关于文件大小的格式提供者的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!
public static class ExtensionMethods
{
public static string ToFileSize(this long l)
{
return String.Format(new FileSizeFormatProvider(),{0:fs},l);
}
}
long l = 100000000;
Console.WriteLine(l.ToFileSize());
public static string GetFileSizeString(string filePath)
{
FileInfo info = new FileInfo(@"c:\windows\notepad.exe");
long size = info.Length;
string sizeString = size.ToString(FileSizeFormatProvider); // This is where the class does its magic...
}
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();
}
}
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);
}
}
long l = 100000000;
Console.WriteLine(l.ToFileSize());