private void button4_Click(object sender, EventArgs e)
        {
            if (validation() == 0)
            {
                errorProvider1.Clear();


                con.Open();
                SqlCommand cmd = con.CreateCommand();
                cmd.CommandType = CommandType.Text;
                cmd.CommandText = "insert into sale_order values ('" + textBox8.Text + "','" + textBox11.Text + "','" + textBox2.Text + "','" + this.dateTimePicker1.Text + "','" + textBox3.Text + "','" + textBox4.Text + "','" + textBox5.Text + "','" + textBox6.Text + "','" + textBox7.Text + "','" + textBox10.Text + "')";
                //cmd.CommandText = "update vehicle set v_quantity = v_quantity - '" + textBox6.Text + "' where v_id = '" + textBox2.Text + "'";
                cmd.ExecuteNonQuery();
                con.Close();


                con.Open();
                SqlCommand cmd1 = con.CreateCommand();
                cmd1.CommandType = CommandType.Text;
                //cmd.CommandText = "insert into sale_order values ('" + textBox8.Text + "','" + textBox11.Text + "','" + textBox2.Text + "','" + textBox3.Text + "','" + textBox4.Text + "','" + textBox5.Text + "','" + textBox6.Text + "','" + textBox7.Text + "','" + textBox10.Text + "')";
                cmd1.CommandText = "update vehicle set v_quantity = v_quantity - '" + textBox6.Text + "' where v_id = '" + textBox2.Text + "'";
                cmd1.ExecuteNonQuery();
                con.Close();



                MessageBox.Show("Added to cart !");
                diplay_data();
                this.Close();
                sale_order so = new sale_order();
                so.Show();
            }
        }
        private void saleOrderToolStripMenuItem_Click(object sender, EventArgs e)
        {
            sale_order sm = new sale_order();

            sm.Show();
        }