(c# + windows forms) Adding items to listBox in different class

Question

I have two classes(forms), and I would like an item from class2 to be added to listBox in class1 when I click \"Accept\" button.

I

Answer 1

You need to access the open form instead of creating new instance of CarRental form

private void button1_Click(object sender, EventArgs e)
{
    CarRental i = (CarRental)Application.OpenForms["CarRentalFormObjectName"];
    string id = idRental.Text.ToString();

    i.listBox1.Items.Add(id);
    i.listBox1.Update();
    this.Close();
}