public static void AddButton(this ApplicationBar appBar, string text, string iconUri, Action clickAction = null)
{
appBar.AddButton(text, new Uri(iconUri, UriKind.Relative), clickAction);
}
private void AddPlusButton()
{
ApplicationBar.AddButton("Add", new Uri("Images/appbar.add.rest.png", UriKind.Relative), OnPlusButtonClicked);
}