如何在登录屏幕上创建登录限制?

我目前正在尝试用c#设计一个atm机，我对此很陌生。我想我的登录屏幕返回到我的欢迎屏幕后3失败的尝试尝试登录，但我不知道从哪里开始以及如何实现我的代码到我的程序做到这一点。

我的当前代码如下所示为我的登录屏幕:

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;
using System.Data.Common;
namespace bankkk
{
    public partial class FrmLogin : Form
    {
        public FrmLogin()
        {
            InitializeComponent();
        }
        public static OleDbConnection con = new OleDbConnection();
        string dbProvider;
        string dbSource;
        OleDbDataAdapter da;
        public static DataSet ds1 = new DataSet();
        string sql;
        string pin;
        int rownum = 0;
        bool valid = false;
        private void FrmLogin_Load(object sender, EventArgs e)
        {
            dbProvider = "PROVIDER=Microsoft.ACE.OLEDB.12.0;";
            dbSource = "Data Source = 'd:''bank11.accdb'";
            con.ConnectionString = dbProvider + dbSource;
            ds1 = new DataSet();
            con.Open();
            sql = " SELECT tblCustomers.* FROM tblCustomers";
            da = new OleDbDataAdapter(sql, con);
            rownum = da.Fill(ds1, "tblCustomers");
            con.Close();
        }
        private void btnexit_Click(object sender, EventArgs e)
        {
            System.Environment.Exit(0);
            this.Close();
        }

        //METHOD VALIDATE
        private bool validate()
        {
            ds1 = new DataSet();
            con.Open();
            sql = "SELECT tblCustomers.* FROM tblCustomers WHERE ((tblCustomers.AccountNo) = '" + txtAccount.Text + "')";
            da = new OleDbDataAdapter(sql, con);
            rownum = da.Fill(ds1, "tblCustomers");
            con.Close();
            if (rownum != 1)
            {
                MessageBox.Show("Not a valid Account");
                return false;
            }
            else
            {
                pin = ds1.Tables["tblCustomers"].Rows[0][4].ToString();
                if (pin == txtPin.Text)
                {
                    return true;
                }
                else
                {
                    MessageBox.Show("INVALID PIN");
                    return false;
                }
            }
        }
        private void btnLogin_Click(object sender, EventArgs e)
        {
            valid = validate();
            if (valid == true)
            {
                if (txtAccount.Text == "11111111" && txtPin.Text == "9999")
                {
                    Frmmanager Manager = new Frmmanager();
                    this.Close();
                    Manager.Show();
                }
                else
                {
                    frmaccount account = new frmaccount();
                    this.Close();
                    account.Show();
                    {
                        txtAccount.Clear();
                        txtPin.Clear();
                    }
                }
            }
        }
        private void btnlogin_Click_1(object sender, EventArgs e)
        {
            valid = validate();
            if (valid == true)
            {
                if (txtAccount.Text == "11111111" && txtPin.Text == "9999")
                {
                    Frmmanager Manager = new Frmmanager();
                    this.Close();
                    Manager.Show();
                }
                else
                {
                    frmaccount account = new frmaccount();
                    this.Close();
                    account.Show();
                    {
                        txtAccount.Clear();
                        txtPin.Clear();
                    }
                }
            }
        }
    }
}

public partial class FrmWelcome {
    //in some part of your code...
    var frmLogin = new FrmLogin();
    //when the login form is closed, show this one.
    //Depending on your application, you might want to add some boolean variable
    //to the Login Form that will be true if the user authentication failed, and 
    //show this form again only if it is true.
    frmLogin.Closed += (s, e) => this.Show();
    this.Hide();
    frmLogin.Show();
}

namespace bankkk
{
    public partial class FrmLogin : Form
    {
        public FrmLogin()
        {
            InitializeComponent();
        }
        ...
        int failedAttempts = 0;
        private void btnlogin_Click_1(object sender, EventArgs e)
        {
            valid = validate();
            if (!valid) {
                //Increment the number of failed attempts
                failedAttempts += 1;
                //If equal to 3
                if (failedAttempts == 3) {
                    //Just close this window
                    this.Close();
                }
            }
            else
            {
                //the same code you were using...
            }
        }
    }
}