Поисковик файлов по его содержимому в разных каталогах

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
 
namespace task_1 {
    class Program
    {
 
    static readonly string searchPattern = "123";
    static readonly string sDir = @"D:\F";
    static int threads;
 
    static void Main (string[] args) {
 
      search(sDir);
 
      while (threads != 0) {
        Thread.Sleep(1000);
      }
    }
 
    async static void search (string path) {
 
      string firstDirectory = "";
      bool isSecondDirectory = false;
 
      foreach (string f in Directory.EnumerateFiles(path, "*", SearchOption.TopDirectoryOnly)) {
        foreach (string line in File.ReadLines(f)) {
          if (line.IndexOf(searchPattern) != -1) {
            Console.WriteLine(f);
            break;
          }
        }
      }
 
      try {
 
        foreach (string d in Directory.EnumerateDirectories(path, "*", SearchOption.TopDirectoryOnly)) {
          if (isSecondDirectory && firstDirectory.Length != 0) {
 
            threads++;
            await Task.Run(() => search(firstDirectory, d));
 
            firstDirectory = "";
            isSecondDirectory = false;
 
          } else if (isSecondDirectory) {
 
            threads++;
            await Task.Run(() => search(d));
 
            isSecondDirectory = false;
            firstDirectory = "";
 
          } else {
 
            firstDirectory = d;
            isSecondDirectory = true;
 
          }
        }
 
      } catch(UnauthorizedAccessException ex) {
        Console.WriteLine(ex.Message);
      }
 
    }
 
    static void search (string path1, string path2) {
 
      search(path1);
      search(path2);
 
      threads--;
 
    }
  }
}