private void button1_Click(object sender, EventArgs e)
 {
     prod = new Product();
     AddEditForm addForm = new AddEditForm(prod, true);
     if (addForm.ShowDialog() == DialogResult.OK)
     {
         listBox1.Items.Add(prod);
     }
 }
        private void button2_Click(object sender, EventArgs e)
        {
            if (listBox1.SelectedIndex == -1)
            {
                MessageBox.Show("Product no chose");
                return;
            }
            int n = listBox1.SelectedIndex;
            prod = (Product)listBox1.Items[n];

            AddEditForm editFrom = new AddEditForm(prod, false);
            editFrom.ShowDialog();

            listBox1.Items.RemoveAt(n);
            listBox1.Items.Insert(n , prod);
            listBox1.SelectedIndex = n;
        }