Build Windows Directories Tree

namespace BuildDirectoriesTree
{
    using System;
    using System.IO;

    /// <summary>
    /// Define classes File { string name, int size } and Folder { string name, File[] files, Folder[] childFolders } and using them build a tree keeping all files and folders on the hard drive starting from C:\WINDOWS. Implement a method that calculates the sum of the file sizes in given subtree of the tree and test it accordingly. Use recursive DFS traversal.
    /// </summary>
    public class BuildDirectoriesTree
    {
        public static void Main()
        {
            string rootDirectory = @"C:\Windows";
            string dirName = "Windows";
            Folder main = new Folder(dirName);
            Folder tree = Tree.TraverseDirectory(rootDirectory, ref main);
            long sum = Tree.CalculateFilesSum(tree);

            Console.WriteLine("The total size of the files is: {0} bytes", sum);
        }
    }

    public class File
    {
        public File(string name, long size)
        {
            this.Name = name;
            this.Size = size;
        }

        public File(string name) : this(name, 0)
        {
        }

        public string Name { get; set; }

        public long Size { get; set; }
    }

    public class Folder
    {
        public Folder(string name)
        {
            this.Name = name;
        }

        public string Name { get; set; }

        public File[] Files { get; set; }

        public Folder[] ChildFolders { get; set; }
    }

    public class Tree
    {
        public static Folder TraverseDirectory(string path, ref Folder root)
        {
            DirectoryInfo directory = new DirectoryInfo(path);
            string directoryName = directory.Name;
            root = new Folder(directoryName);

            FileInfo[] currentDirectoryFiles = directory.GetFiles();
            root.Files = new File[currentDirectoryFiles.Length];

            for (int i = 0; i < currentDirectoryFiles.Length; i++)
            {
                string fileName = currentDirectoryFiles[i].Name;
                long length = currentDirectoryFiles[i].Length;

                root.Files[i] = new File(fileName, length);
            }

            DirectoryInfo[] currentDirectorySubDirectories = directory.GetDirectories();
            root.ChildFolders = new Folder[currentDirectorySubDirectories.Length];

            for (int i = 0; i < currentDirectorySubDirectories.Length; i++)
            {
                try
                {
                    string dirName = currentDirectorySubDirectories[i].Name;
                    path = currentDirectorySubDirectories[i].FullName;
                    Folder currentSubFolder = new Folder(dirName);
                    TraverseDirectory(path, ref currentSubFolder);
                    root.ChildFolders[i] = currentSubFolder;
                }
                catch (System.UnauthorizedAccessException)
                {
                    continue;
                }
            }

            return root;
        }

        public static long CalculateFilesSum(Folder folder)
        {
            long currentSum = 0;
            foreach (var file in folder.Files)
            {
                currentSum += file.Size;
            }

            foreach (var childFolder in folder.ChildFolders)
            {
                long childSum = CalculateFilesSum(childFolder);
                currentSum += childSum;
            }

            return currentSum;
        }
    }
}