Combo box depends on another combo box

table1       table2

option1      displaysthis1
option2      displaysthis2
option3      displaysthis3

void Fillcombo() {
            string newcontact = "datasource=localhost;port=3306;username=root;password=password";
            string Query = "select * from database.clients ;";

            MySqlConnection addcon = new MySqlConnection(newcontact);
            MySqlCommand cmdDataBase = new MySqlCommand(Query, addcon);
            MySqlDataReader myReader;

            try
            {
                addcon.Open();
                myReader = cmdDataBase.ExecuteReader();
           
                
                while (myReader.Read())
                {
                    string sName = myReader.GetString("company");
                    comboBox1.Items.Add(sName);
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }