one of the listbox data is transfer to another listbox

Hi,
I have only string tyes in my listbox and below code works for me
private void addButton_Click(object sender, EventArgs e)
{
//Adding to 2nd listbox
foreach (string item in listBox1.SelectedItems)
{
listBox2.Items.Add(item);

}
//Removing from 1st list box, items which added to 2nd list box
foreach (string item in listBox2.Items)
{
listBox1.Items.Remove(item);
}
}
private void button1_Click_1(object sender, EventArgs e)
{
//Adding to 1st listbox, items which selected in 2nd listbox
foreach (string item in listBox2.SelectedItems)
{
listBox1.Items.Add(item);
}
//Removing from 2nd list box, items selected
foreach (string item in listBox1.Items)
{
listBox2.Items.Remove(item);
}
}