void ListView1_ButtonReleased(object sender, ButtonEventArgs e)
{
if (e.Button == PointerButton.Right)
{
editMenuItem.Visible = button_edit.Sensitive;
addMenuItem.Visible = button_plus.Sensitive;
removeMenuItem.Visible = button_minus.Sensitive;
upMenuItem.Visible = button_up.Sensitive;
downMenuItem.Visible = button_down.Sensitive;
listMenu.Popup();
}
}