MainForm C#

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 Npgsql;

namespace WindowsFormsApp2
{
    public partial class Form1 : Form
    {
        NpgsqlConnection con = new NpgsqlConnection("Server=127.0.0.1;Port=5432;User Id=postgres;Password=12436Dark;Database=usersroles;");
        public Form1()
        {

            //this.ControlBox = false;
            InitializeComponent();
            txbPass.UseSystemPasswordChar = true;
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {

        }

        private void btReg_Click(object sender, EventArgs e)
        {
            this.Hide();
            Reg rg = new Reg();
            rg.Show();
        }

        private void btAuth_Click(object sender, EventArgs e)
        {
            string nowDate = DateTime.Now.ToShortDateString();
            string nowTime = DateTime.Now.ToShortTimeString();
            con.Open();
            string username, password;
            username = txbLogin.Text;
            password = txbPass.Text;
            NpgsqlCommand com = new NpgsqlCommand("select count(*) from users where username = @user and password = @pass", con);
            com.Parameters.Add("user", NpgsqlTypes.NpgsqlDbType.Char, 30).Value = username;
            com.Parameters.Add("pass", NpgsqlTypes.NpgsqlDbType.Char, 30).Value = password;
            int res = Convert.ToInt32(com.ExecuteScalar());
                if(res == 1){
                NpgsqlCommand com1 = new NpgsqlCommand("select userid from users where username = @user and password = @pass", con);
                com1.Parameters.Add("user", NpgsqlTypes.NpgsqlDbType.Char, 30).Value = username;
                com1.Parameters.Add("pass", NpgsqlTypes.NpgsqlDbType.Char, 30).Value = password;
                int n = Convert.ToInt32(com1.ExecuteScalar());
                Prog pr = new Prog(n);
                this.Hide();
                pr.Show();

                NpgsqlCommand cmd = new NpgsqlCommand("INSERT INTO \"journal\" (\"date\", \"time\", \"user\", \"action\") VALUES (@date, @time, @user, @act)", con);
                cmd.Parameters.Add("date", NpgsqlTypes.NpgsqlDbType.Date).Value = DateTime.Parse(nowDate);
                cmd.Parameters.Add("time", NpgsqlTypes.NpgsqlDbType.Time).Value = DateTime.Parse(nowTime);
                cmd.Parameters.Add("user", NpgsqlTypes.NpgsqlDbType.Bigint).Value = n;
                cmd.Parameters.Add("act", NpgsqlTypes.NpgsqlDbType.Bigint).Value = 1;
                cmd.ExecuteNonQuery();


            }
            else
            {
                NpgsqlCommand cmd = new NpgsqlCommand("select userid from users where username = @user ", con);
                cmd.Parameters.Add("user", NpgsqlTypes.NpgsqlDbType.Char, 30).Value = username;
                int mn = Convert.ToInt32(cmd.ExecuteScalar());
                if (mn >0)
                {
                    NpgsqlCommand cmd1 = new NpgsqlCommand("INSERT INTO \"journal\" (\"date\", \"time\", \"user\", \"action\") VALUES (@date, @time, @user, @act)", con);
                    cmd1.Parameters.Add("date", NpgsqlTypes.NpgsqlDbType.Date).Value = DateTime.Parse(nowDate);
                    cmd1.Parameters.Add("time", NpgsqlTypes.NpgsqlDbType.Time).Value = DateTime.Parse(nowTime);
                    cmd1.Parameters.Add("user", NpgsqlTypes.NpgsqlDbType.Bigint).Value = mn;
                    cmd1.Parameters.Add("act", NpgsqlTypes.NpgsqlDbType.Bigint).Value = 6;
                    cmd1.ExecuteNonQuery();
                }
                MessageBox.Show("Такого пользователя не существует или пароль введен неверно!", "Ошибка!");
                }

            con.Close();
        }

        private void btLook_Click(object sender, EventArgs e)
        {
            if (txbPass.UseSystemPasswordChar == true)
            {
                txbPass.UseSystemPasswordChar = false;
            }
            else
            {
                txbPass.UseSystemPasswordChar = true;
            }
        }
    }
    class l
    {
        public string Code { get; set; }
        public string Name { get; set; }
    }
}