private void DisplayData()
        {
            //connection
            SqlConnection connString = DbHandler.GetConnection();

            try
            {
                connString.Open();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception in DBHandler", ex);
            }
            //select all data from line table
            string getLinecommand = "Select * From Line";

            lineDataAdapter = new SqlDataAdapter(getLinecommand, connString);
            //select all data from line table
            string getStationcommand = "Select * From Station";

            stationDataAdapter = new SqlDataAdapter(getStationcommand, connString);
            //fill the table
            this.stationDataAdapter.Fill(
                this.stationDataSet.Station);
            this.lineDataAdapter.Fill(
                this.lineDataset.Line);
        }
        public AddLineandStation()
        {
            InitializeComponent();
            //connection
            SqlConnection connString = DbHandler.GetConnection();

            try
            {
                connString.Open();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception in DBHandler", ex);
            }
            string trainLine = lineTextbox.Text;

            DisplayData();
        }
        private void addLineButton_Click(object sender, EventArgs e)
        {
            string trainLine = lineTextbox.Text;
            //connection
            SqlConnection connString = DbHandler.GetConnection();

            try
            {
                connString.Open();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception in DBHandler", ex);
            }
            // select every row in line table for name column which is the input of train line textbox
            string     myQuery   = "Select * From Line Where Name = '" + trainLine + "'";
            SqlCommand myCommand = new SqlCommand(myQuery, connString);

            myCommand.ExecuteNonQuery();
            SqlDataReader dataReader = myCommand.ExecuteReader();

            //if the train line exists in the database then output a message
            if (dataReader.HasRows)
            {
                outputLabel.Text = "Train line already exists";
            }

            else
            {
                try
                {
                    //if not then add the data in child table
                    DbHandler.AddLine(trainLine);
                    outputLabel.Text = "Train line added Successfully!";
                    DisplayData();
                    ClearData();
                    MessageBox.Show("Successfully data added!");
                }
                catch (Exception ex)
                {
                    outputLabel.Text = "Error!" + ex;
                }
            }
        }