Selecting Listview items then App is Crashed.

problem is that when i add item in listview, its properly add then i select any item in Listview So app crashed. i don't understand and i also use try/catch but no solve this problem.

Code Behind is

List ss;

public AddMenuPage()

{

InitializeComponent();

ss =new List() { "Awesome!", "Great!", "Cool!", "Good!", "Not Bad!", "Meh!", "Awesome!", "Great!", "Cool!", "Good!", "Not Bad!", "Meh!" };

SelectionListView.ItemsSource = ss;

}

private void Button_Clicked(object sender, EventArgs e)

{

try

{

ss.Add("amit");

SelectionListView.ItemsSource = ss;

}

catch (Exception ex)

{

}