private void Login_Click(object sender, EventArgs e)
        {
            var passMd5 = Cnst.ToMd5(txtPassword.Text.Trim()); // pass pakeistas i md5 hash
            var query   = "Select * from tblLogin Where username = '******' and password = '******'";
            var sda     = new SqlDataAdapter(query, Cnst.SqlCon);
            var dtbl    = new DataTable();

            sda.Fill(dtbl);
            if (dtbl.Rows.Count == 0)
            {
                MessageBox.Show("Check username and (or) password");
            }
            else
            {
                Cnst.User   = txtUserName.Text.Trim();
                Cnst.alevel = Int32.Parse(dtbl.Rows[0]["level"].ToString()); // authorization level
                switch (Cnst.alevel)
                {
                case 0:
                {
                    var redirect = new PardavejoMeniu();
                    Hide();
                    redirect.Show();
                    break;
                }

                case 1:
                {
                    var redirect = new SandelininkoMeniu();
                    Hide();
                    redirect.Show();
                    break;
                }

                case 2:
                {
                    var redirect = new AdministratoriausMeniu();
                    Hide();
                    redirect.Show();
                    break;
                }
                }
            }
        }
        private void button1_Click(object sender, EventArgs e)
        {
            switch (Cnst.alevel)
            {
            case 0:
            {
                var redirect = new PardavejoMeniu();
                Hide();
                redirect.Show();
                break;
            }

            case 1:
            {
                var redirect = new SandelininkoMeniu();
                Hide();
                redirect.Show();
                break;
            }

            case 2:
            {
                var redirect = new AdministratoriausMeniu();
                Hide();
                redirect.Show();
                break;
            }

            default:
            {
                var redirect = new Prisijungimas();
                Hide();
                redirect.Show();
                break;
            }
            }
        }