Get file sizes by there extensions

gistfile1.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace FileHlpr
{
    internal class FileInformation
    {
        public string Filename { get; set; }
        public string Ext { get; set; }
        public long Size { get; set; }
    }

    internal class FileResult
    {
        public string Ext { get; set; }
        public long SummarySize { get; set; }
        public long Count { get; set; }
    }

    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();
        }

    }

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

    class Program
    {
        static void Main(string[] args)
        {
            var files = System.IO.Directory.EnumerateFiles(Directory.GetCurrentDirectory(), "*.*", SearchOption.AllDirectories);

            var maps = from fileName in files.Where(file => !file.Contains(".hg"))
                      select new FileInformation()
                          {
                              Filename = fileName,
                              Ext = Path.GetExtension(fileName).ToLowerInvariant(),
                              Size = new FileInfo(fileName).Length
                          };
            
            var res = from map in maps
                      group map by map.Ext
                      into g
                      select new FileResult()
                          {
                              Ext = g.Key,
                              Count = g.Count(),
                              SummarySize = g.Sum(f => f.Size)
                          };

            foreach (var result in res.OrderByDescending(r => r.SummarySize))
            {

                Console.WriteLine("{0} Count: {1}, SummarySize: {2}", result.Ext, result.Count, result.SummarySize.ToFileSize());
            }    
        }
    }
}