Question

Is there any easy way to create a class that uses IFormatProvider that writes out a user-friendly file-size?

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... } 

It should result in strings formatted something like ‘2,5 MB‘, ‘3,9 GB‘, ‘670 bytes‘ and so on.

Answer 1

I use this one, I get it from the web

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();     }  } 

an example of use would be:

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

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:

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

You can use it like this.

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