Directory Traversal

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

class Program
{
    static void Main()
    {
        string directory = Console.ReadLine();
        SortedDictionary<string, Dictionary<string, double>> extensions = new SortedDictionary<string, Dictionary<string, double>>();
        DirectoryInfo directorySelected = new DirectoryInfo(directory);
        FileInfo[] whole = directorySelected.GetFiles();

        GetFileExtensions(extensions, whole);

        GroupAndWrite(extensions);

    }
    static void GroupAndWrite(SortedDictionary<string, Dictionary<string, double>> extensions)
    {
        var orderedExtension = extensions.OrderByDescending(p => p.Value.Count).ThenBy(ext => ext.Key);
        using (StreamWriter destination = new StreamWriter(@"C:\Users\asus\Desktop\text.txt"))
        {
            foreach (var item in orderedExtension)
            {
                destination.WriteLine(item.Key);
                var orderedDic = item.Value.OrderBy(f => f.Value);
                foreach (var output in orderedDic)
                {
                    destination.WriteLine("{0}{1}kb", output.Key, output.Value / 1024);
                }
            }
        }
    }
    static void GetFileExtensions(SortedDictionary<string, Dictionary<string, double>> extensions, FileInfo[] files)
    {
        foreach (var n in files)
        {
            if (!extensions.ContainsKey(n.Extension))
            {
                extensions.Add(n.Extension, new Dictionary<string, double>
                                    {{string.Format("--{0} - ", n.Name), n.Length}});
            }
            else
            {
                extensions[n.Extension].Add(string.Format("--{0} - ", n.Name), n.Length);
            }
        }
    }
}