ListViewItem[] items = new ListViewItem[listView1.Items.Count];
int i = 0;
foreach (ListViewItem item in listView1.Items)
{
items[i++] = (ListViewItem)item.Clone();
}
listView2.Items.AddRange(items);
int i = 0;
foreach (ListViewItem item in listView1.Items)
{
items[i++] = (ListViewItem)item.Clone();
}
listView2.Items.AddRange(items);