private void bt_Login_Click(object sender, EventArgs e)
        {
            MY_DB dB = new MY_DB();

            string str_command;

            SqlDataAdapter adapter = new SqlDataAdapter();
            DataTable      table   = new DataTable();

            if (radioButtonStudent.Checked == true)
            {
                str_command = "SELECT * FROM login WHERE username = @User AND password = @Pass";
            }
            else
            {
                str_command = "SELECT * FROM users WHERE username = @User AND password = @Pass";
            }
            SqlCommand command = new SqlCommand(str_command, dB.GetConnection);

            command.Parameters.Add("@User", SqlDbType.VarChar).Value = TextBoxUsername.Text;
            command.Parameters.Add("@Pass", SqlDbType.VarChar).Value = TextBoxPassword.Text;

            adapter.SelectCommand = command;
            adapter.Fill(table);

            if (table.Rows.Count > 0)
            {
                //MessageBox.Show("Ok, next time will be go to Main Menu of App");
                this.Hide();
                if (radioButtonStudent.Checked == true)
                {
                    Main_Form main = new Main_Form();
                    main.ShowDialog(this);
                    this.Close();
                }
                else
                {
                    HumanResourceForm human = new HumanResourceForm();
                    int userid = Convert.ToInt32(table.Rows[0][0].ToString());
                    Globals.setGlobalUserId(userid);
                    human.ShowDialog(this);
                }
            }
            else
            {
                MessageBox.Show("Invalid Username Or Password", "Login Error", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }
        bool check_sys()
        {
            // Kiểm tra ID và User đã có trên hệ thống chưa
            MY_DB db = new MY_DB();

            SqlDataAdapter adapter  = new SqlDataAdapter();
            DataTable      table    = new DataTable();
            SqlCommand     commmand = new SqlCommand("SELECT * FROM dbo.users WHERE uid = @Id OR username = @Username", db.GetConnection);

            commmand.Parameters.Add("@Id", SqlDbType.Int).Value         = Convert.ToInt32(textBoxIDUser.Text);
            commmand.Parameters.Add("@Username", SqlDbType.NChar).Value = textBoxUsername.Text.Trim();
            adapter.SelectCommand = commmand;
            adapter.Fill(table);
            if (table.Rows.Count > 0)// Đã có id hoặc user trên hệ thống
            {
                return(true);
            }
            return(false);
        }