Get Active Active Directory Users based on List of usernames

ADUtils.cs

using System;
using System.Linq;
using System.Collections.Generic;
using System.DirectoryServices;
using BrunoMartinsPro.Data.Interfaces.Utils.ActiveDirectory;

namespace BrunoMartinsPro.Utils.ActiveDirectory
{
    public class ADUtils : IADUtils
    {
        private readonly DirectoryEntry _directoryEntry;
        
        public ActiveDirectoryUtils(DirectoryEntry directoryEntry)
        {
            _directoryEntry = directoryEntry;
        }

        /// <summary>
        /// Get all ActiveDirectory Users
        /// </summary>
        public List<string> GetActiveDirectoryUsers(List<string> existingUsernameList)
        {
            List<string> users = new List<string>();

            var usernameQuery = $"(|{String.Join(string.Empty, existingUsernameList.Select(x => $"(SAMAccountName=*{x}*)").ToList())})"; 

            //Create Directory Search
            DirectorySearcher search = new DirectorySearcher(_directoryEntry);
            
            //Search for a user that is member of anything and is active
            string query = $"(&(objectCategory=person)(objectClass=user)(!userAccountControl:1.2.840.113556.1.4.803:=2){usernameQuery})";

            //Apply search query
            search.Filter = query;

            //Add property SAM ACCOUNT NAME
            search.PropertiesToLoad.Add("samaccountname");

            //Execute search
            SearchResultCollection mySearchResultColl = search.FindAll();
            
            //Add users
            foreach (SearchResult result in mySearchResultColl)
            {
                //Get user
                var userToAdd = result.Properties["samaccountname"][0].ToString();

                //Add user
                users.Add(userToAdd);
            }

            //return users
            return users;
        }
    }
}

IADUtils.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace BrunoMartinsPro.Data.Interfaces.Utils.ActiveDirectory
{
    public interface IADUtils
    {
        List<string> GetActiveDirectoryUsers(List<string> existingUsernameList);
    }
}