How to send form 1 listbox items to form 2 listbox items

See more:

C#

ListBox

forms

I want to :
When i click a button (xuiButton2) it opens a new form 2
it worked
and in form 2 there is a listbox
the items in that listbox are the same than the items in the other listbox

What I have tried:

I tried making that when alertfullscreen (my form 2) load it adds in listBox1 the items from the listBox1 of Form 1 but it didn't worked

Form 1:

private void xuiButton2_Click(object sender, EventArgs e)
{
    alertfullscreen form2 = new alertfullscreen();
    form2.Show();
}

form 2 :

private void alertfullscreen_Load(object sender, EventArgs e)
        {
            listBox1.Items = Form1.listBox1.Items;
        }