ติดปัญหา insert Foreign key ค่ะรับค่าลงหลายตารางและต้องเก็บ FK ด้วย ใช้ VS2010 C#

        protected void btnSave_Click(object sender, EventArgs e)   
        {                                                          
            SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["BD_TrainingConnectionString"].ConnectionString);
            con.Open();
            SqlCommand com = new SqlCommand("insert into Trainners(T_name, T_company, T_phone, T_descrip)values(@T_name, @T_company, @T_phone, @T_descrip)", con);
            com.CommandType = CommandType.Text;
            com.Parameters.AddWithValue("T_name", txtcouTrainner.Text);
            com.Parameters.AddWithValue("T_company", txtcouCompany.Text);
            com.Parameters.AddWithValue("T_phone", txtPhone.Text);
            com.Parameters.AddWithValue("T_descrip", txtDescrip.Text);            
            com.ExecuteNonQuery();
            con.Close();

            con.Open();
            SqlCommand com2 = new SqlCommand("insert into Prices(price_01, price_02, price_03, price_04, price_05, price_06, price_07, price_08, price_09, price_10, price_11, price_12, price_13, price_14, price_15, price_16, result)"
                                            +"values(@price_01, @price_02, @price_03, @price_04, @price_05, @price_06, @price_07, @price_08, @price_09, @price_10, @price_11, @price_12, @price_13, @price_14, @price_15, @price_16, @result)", con);
            com2.CommandType = CommandType.Text;
            com2.Parameters.AddWithValue("price_01", txtP01.Text);
            com2.Parameters.AddWithValue("price_02", txtP02.Text);
            com2.Parameters.AddWithValue("price_03", txtP03.Text);
            com2.Parameters.AddWithValue("price_04", txtP04.Text);
            com2.Parameters.AddWithValue("price_05", txtP05.Text);
            com2.Parameters.AddWithValue("price_06", txtP06.Text);
            com2.Parameters.AddWithValue("price_07", txtP07.Text);
            com2.Parameters.AddWithValue("price_08", txtP08.Text);
            com2.Parameters.AddWithValue("price_09", txtP09.Text);
            com2.Parameters.AddWithValue("price_10", txtP10.Text);
            com2.Parameters.AddWithValue("price_11", txtP11.Text);
            com2.Parameters.AddWithValue("price_12", txtP12.Text);
            com2.Parameters.AddWithValue("price_13", txtP13.Text);
            com2.Parameters.AddWithValue("price_14", txtP14.Text);
            com2.Parameters.AddWithValue("price_15", txtP15.Text);
            com2.Parameters.AddWithValue("price_16", txtP16.Text);
            com2.Parameters.AddWithValue("result", txtCost.Text);
            com2.ExecuteNonQuery();
            con.Close(); 

            
            string fk1 = "Select MAX(TID) From Trinners";
            string fk2 = "Select MAX(priceID) From Prices";
            int tid, pid;
            tid = Convert.ToInt32(fk1);
            pid = Convert.ToInt32(fk2);

            String cou_type = null;

            if (rdInternal.Checked == true)
            {
                cou_type = rdInternal.Text;
            }
            else if (rdExternal.Checked == true)
            {
                cou_type = rdExternal.Text;
            }
                con.Open();
                SqlCommand com3 = new SqlCommand("insert into Courses(cou_name,cou_type,cou_location,cou_date,cou_todate,cou_hour,TID,priceID)"
                                                +"values(@cou_name,@cou_type,@cou_location,@cou_date,@cou_todate,@cou_hour, @tid, @pid)", con);
                com3.CommandType = CommandType.Text;
                com3.Parameters.AddWithValue("cou_name", txtcouName.Text);
                com3.Parameters.AddWithValue("cou_type",cou_type);
                com3.Parameters.AddWithValue("cou_location", txtcouLocation.Text);
                com3.Parameters.AddWithValue("cou_date", DateTime.ParseExact(txtDate.Text.ToString(), "dd/MM/yyyy", CultureInfo.InvariantCulture));
                com3.Parameters.AddWithValue("cou_todate", DateTime.ParseExact(txtTodate.Text.ToString(), "dd/MM/yyyy", CultureInfo.InvariantCulture));
                com3.Parameters.AddWithValue("cou_hour", txtcouTime.Text);
                com3.Parameters.AddWithValue("TID", Convert.ToInt32(fk1));
                com3.Parameters.AddWithValue("priceID", Convert.ToInt32(fk2));
                com3.ExecuteNonQuery();
                Label1.Text = "Record Successfully";
                Response.Redirect("Course.aspx");
        }