How to perform Hold event in Windows Phonw 8?

How to perform Hold event in Windows Phonw 8?

I'm trying to deal with hold event on my Windows Phone 8 project.
This is my list's tap event
private void lstData_Tap(object sender,
System.Windows.Input.GestureEventArgs e)
{
Bus selectedItemData = (sender as ListBox).SelectedItem as Bus;
if (selectedItemData != null)
{
var num = selectedItemData.Number;
var route = selectedItemData.Route;
NavigationService.Navigate(new
Uri(string.Format("/Details.xaml?parameter1=" + num +
"&parameter2=" + route), UriKind.Relative));
}
And this is Hold event
private void lstData_Hold(object sender,
System.Windows.Input.GestureEventArgs e)
{
MessageBoxResult m = MessageBox.Show("Would you like to add this
bus to favorite list", "Add to Favorite",
MessageBoxButton.OKCancel);
if(m==MessageBoxResult.OK)
{
Bus selectedItemData2 = (sender as ListBox).SelectedItem as Bus;
if (selectedItemData2 != null)
{
MessageBox.Show(selectedItemData2.Route);
}
}
}
The problem is that selectedItemData2 in Hold event comes null when I
debugged. I can't understand how it is possible that it work for tap event
but not for hold event. Please help me!