void OnItemSelected(object sender, SelectedItemChangedEventArgs e)
{
var audioItem = e.SelectedItem as AudioItem;
var audioPage = new AudioItemPage();
audioPage.BindingContext = audioItem;
Navigation.PushAsync(audioPage, true);
}
void OnAddItemClicked(object sender, EventArgs e)
{
var audioItem = new AudioItem();
audioItem.Username = (string)App.Current.Properties["Username"];
var audioPage = new AudioItemPage(true);
audioPage.BindingContext = audioItem;
Navigation.PushAsync(audioPage, true);
}