c# coding error trapping help

JimmyJimJam · February 2, 2017

so I'm trying to error trap a certain piece of code so that you cannot continue without the combo boxes having data selected in them.

any time I try to continue the error message saying for me to select the data comes up even after I have selected it.

public bool IsPresentCBO(ComboBox cbo, string name)
{
if (cbo.SelectedItem == null);

            {
                MessageBox.Show("Please select one of the following - " + name);
                cbo.Focus();
                return false;
            }
            return true;
        }
        public bool IsValidData()
        {
            return

            IsPresentCBO(cbo_class, "seating class ") &&
            IsPresentCBO(cbo_location, "location ") &&
            IsPresentCBO(cbo_tickets, "tickets ");
        }

private void textBox1_TextChanged(object sender, EventArgs e)
{

            string location = cbo_location.SelectedItem.ToString();
            int price = 0;
            switch (location)
            {
                case "Tokyo":
                    price = 900;
                    break;

                case "London":
                    price = 120;
                    break;

                case "Paris":
                    price = 260;
                    break;

                case "New york":
                    price = 700;
                    break;
            }
            string Flightclasses = cbo_class.SelectedItem.ToString();
            int price1 = 0;
            switch (Flightclasses)
            {
                case "Economy":
                    price = 50;
                    break;

                case "First class":
                    price = 120;
                    break;

                case "Business":
                    price = 80;
                    break;
            }

decimal totalprice = price + price1 * price;
txt_flightcost.Text = totalprice.ToString("c");