private void btnDangNhap_Click(object sender, EventArgs e) { //aa DBConnect cn = new DBConnect(); string txtID = txtId.Text; string txtPass = txtPASS.Text; EmployeeManagement employee = new EmployeeManagement(); cn.conn.Open(); if (employee.CheckLogin(txtID, txtPass) == 3) { frmNhanVien NV = new frmNhanVien(); NV.Show(); } else if (employee.CheckLogin(txtID, txtPass) == 0) { MessageBox.Show("Dữ liệu không hợp lệ"); } else { frmQuanLi QL = new frmQuanLi(); QL.Show(); } cn.conn.Close(); }