DuplicateFinder/Program.cs

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

namespace DuplicateFinder
{
    internal class Program
    {
        private static string CalculateSha1(string filePath)
        {
            using (var sha1 = SHA1.Create())
            {
                using (var stream = File.OpenRead(filePath))
                {
                    byte[] hashBytes = sha1.ComputeHash(stream);
                    return BitConverter.ToString(hashBytes).Replace("-", "").ToLower();
                }
            }
        }

        static string GetValidDirectoryPath()
        {
            Console.Write("Enter directory path: ");
            string path = Console.ReadLine().Trim();
            if (!Directory.Exists(path))
            {
                Console.WriteLine("The directory does not exist. Please try again.");
                return GetValidDirectoryPath();
            }
            Console.WriteLine();
            return path;
        }

        static void Main(string[] args)
        {
            string directoryPath = GetValidDirectoryPath();

            Dictionary<string, List<string>> fileHashes = new Dictionary<string, List<string>>();
            foreach (string filePath in Directory.EnumerateFiles(directoryPath, "*.*", SearchOption.AllDirectories))
            {
                Console.WriteLine("Calculating hash: " + filePath);
                string hash = CalculateSha1(filePath);
                if (fileHashes.ContainsKey(hash))
                {
                    fileHashes[hash].Add(filePath);
                }
                else
                {
                    fileHashes[hash] = new List<string> { filePath };
                }
            }

            if (fileHashes.Values.Count(v => v.Count > 1) > 1)
            {
                Console.WriteLine("\nDuplicate files:");
                foreach (List<string> group in fileHashes.Values.Where(v => v.Count > 1))
                {
                    foreach (string filePath in group)
                    {
                        Console.WriteLine(filePath);
                    }
                    Console.WriteLine();
                }
            }
            else
            {
                Console.WriteLine("\nDuplicates not find.");
            }

            Console.WriteLine("Press any key to exit...");
            Console.ReadKey();
        }
    }
}