using a combobox and generating an additional window for each option in the combobox

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C#

ADO.NET

hey!

Im developing a student database and would basically like to use windows form applications and sql databases

i want to design a combobox such that when i select an option, a new window appears and has a list of subjects for which i can enter the marks. how do i do this?

code so far is..

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace students
{
    public partial class Form1 : Form
    {
        private SqlConnection con;
        private SqlCommand command;
        private SqlDataAdapter adapter;
        private DataSet dataset;
       

        public Form1()
        {
            InitializeComponent();

            con = new SqlConnection();
            command = con.CreateCommand();
            con.ConnectionString = "Data Source=CASSINI-003-PC;Initial Catalog=studentdb;Integrated Security=True";
            adapter = new SqlDataAdapter(command);
            dataset = new DataSet();
        }

       private void button1_Click(object sender, EventArgs e)
        {
            command.Parameters.AddWithValue("@StudentID", textBox1.Text);
            command.Parameters.AddWithValue("@Name",textBox2.Text);
            command.Parameters.AddWithValue("@Age",textBox3.Text);
            command.Parameters.AddWithValue("@Gender",textBox4.Text);
            command.Parameters.AddWithValue("@Courseno",comboBox1.Text);
            command.CommandText = "INSERT into details" + "(StudentID,Name,Age,Gender,Courseno)VALUES" + "(@StudentID,@Name,@Age,@Gender,@Courseno)";

            try
            {
                con.Open();

                int result = command.ExecuteNonQuery();

                if (result > 0)
                    MessageBox.Show("student successfully updated");
                else
                    MessageBox.Show("failed to update");
            }
            catch (SqlException ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally
            {
                con.Close();
            }

            ClearFields();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            command.Parameters.Clear();
            command.Parameters.AddWithValue("@StudentID", textBox1.Text);
            command.CommandText = "SELECT * FROM details WHERE StudentID=@StudentID";
            

            dataset.Tables.Clear();

            int result = adapter.Fill(dataset, "details");

            if (result > 0)
            {
                DataRow srow = dataset.Tables["details"].Rows[0];
                textBox1.Text = srow["StudentID"].ToString();
                textBox2.Text = srow["Name"].ToString();
                textBox3.Text = srow["Age"].ToString();
                textBox4.Text = srow["Gender"].ToString();
                comboBox1.Text = srow["Courseno"].ToString();
            }
            else
            {
                MessageBox.Show("Student does not exist");
            }
       
        }

        void ClearFields()
        {
            textBox1.Text = String.Empty;
            textBox2.Text = String.Empty;
            textBox3.Text = String.Empty;
            textBox4.Text = String.Empty;
            comboBox1.Text = String.Empty;
        }
}
}