Active Directory in C#

with the help of this code we check user exist or not on given directory.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.DirectoryServices;
using System.DirectoryServices.AccountManagement;
using System.DirectoryServices.ActiveDirectory;
using System.DirectoryServices.Protocols;
using System.Net;


namespace ADCheck
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {

            try
            {
                LdapConnection connection = new LdapConnection(txtad.Text);
                NetworkCredential credential = new NetworkCredential(txtusername.Text, txtpassword.Text);
                connection.Credential = credential;
                connection.Bind();
                Console.WriteLine("logged in");
                MessageBox.Show("Successfully");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }


        }
    }
}