Step by Step solution about How to resolve the algorithm Walk a directory/Recursively step by step in the C# programming language

This code prints the name of each file in a directory tree that matches a file pattern. The code does this by traversing all the subdirectories from a given root directory. It starts by creating a stack of directories to visit. The stack is initially filled with just the root directory.

The code then enters a while loop that continues until the stack is empty. In each iteration of the loop, the code pops the top directory off the stack and tries to get a list of all the files and directories in that directory. If the code doesn't have access to the directory, it skips it and continues to the next directory on the stack.

Once the code has a list of all the files and directories in the current directory, it filters the list of files by the file pattern. The code yields each file that matches the pattern, which means that the file is returned to the caller of the TraverseDirectory function.

The code continues this process until it has visited all the directories in the directory tree. After the code has visited all the directories, it prints the name of each file that it found.

Here is a breakdown of the code:

• The TraverseDirectory function takes two arguments: a root path and a function that takes a FileInfo object and returns a boolean value. The function returns an IEnumerable of FileInfo objects that match the pattern.
• The TraverseDirectory function uses a stack to keep track of the directories that it has yet to visit.
• The TraverseDirectory function uses the GetDirectories and GetFiles methods of the DirectoryInfo class to get a list of all the directories and files in a directory.
• The TraverseDirectory function uses the Where method of the IEnumerable class to filter the list of files by the file pattern.
• The TraverseDirectory function uses the yield return statement to return each file that matches the pattern.
• The Main function calls the TraverseDirectory function to get a list of all the .wmv files in the C:\Windows directory tree.
• The Main function prints the name of each file that was returned by the TraverseDirectory function.

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

namespace RosettaRecursiveDirectory
{
    class Program
    {
        static IEnumerable<FileInfo> TraverseDirectory(string rootPath, Func<FileInfo, bool> Pattern)
        {
            var directoryStack = new Stack<DirectoryInfo>();
            directoryStack.Push(new DirectoryInfo(rootPath));
            while (directoryStack.Count > 0)
            {
                var dir = directoryStack.Pop();
                try
                {
                    foreach (var i in dir.GetDirectories())
                        directoryStack.Push(i);
                }
                catch (UnauthorizedAccessException) {
                    continue; // We don't have access to this directory, so skip it
                }
                foreach (var f in dir.GetFiles().Where(Pattern)) // "Pattern" is a function
                    yield return f;
            }
        }
        static void Main(string[] args)
        {
            // Print the full path of all .wmv files that are somewhere in the C:\Windows directory or its subdirectories
            foreach (var file in TraverseDirectory(@"C:\Windows", f => f.Extension == ".wmv"))
                Console.WriteLine(file.FullName);
            Console.WriteLine("Done.");
        }
    }
}