Login form not working

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.OleDb;

namespace Accreditation
{
    public partial class LoginForm : Form
    {
        public LoginForm()
        {
            InitializeComponent();
        }
        
        private void LoginForm_Load(object sender, EventArgs e)
        {
            this.AcceptButton = btnLogin;
            this.CancelButton = btnCancel;
        }

        int ctr;
        private void btnLogin_Click(object sender, EventArgs e)
        {
            OleDbConnection con = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data Source=Accreditation.mdb; User ID=admin; Password=delhigames;");
            ctr = ctr + 1;
            OleDbDataAdapter adp1 = new OleDbDataAdapter("select * from ComLogin", con);
            DataSet ds1 = new DataSet();
            adp1.Fill(ds1, "ComLogin");
            if (ds1.Tables.Count > 0)
            {
                bool validUser1 = false;
                validUser1 = false;
                foreach (DataRow dr in ds1.Tables[0].Rows)
                {
                    if (dr[0].ToString() == txtUsername.Text && dr[1].ToString() == txtPassword.Text)
                    {
                        validUser1 = true;
                        Visitors frm = new Visitors();
                        this.Hide();
                        frm.Show();
                    }
                }
                if (validUser1 == false)
                {
                    MessageBox.Show("Enter valid User ID/Password!");
                }
            }
            
            else
            {
                if (ctr < 3)
                {
                    MessageBox.Show("Incorrect User Name & Password. Please Try again.");
                    txtUsername.Focus();
                }
                else
                {
                    MessageBox.Show("Unauthorized Access. Aborting..");
                    this.Close();
                }
            }
        }
 
        private void btnCancel_Click(object sender, EventArgs e)
        {
            this.Close();
            Application.Exit();
        }
    }
}