public override UIBarButtonItem[] CreateToolbarItems()
{
var baseButtons = base.CreateToolbarItems();
if (PreviousButtonVisible)
_PrevButton = new UIBarButtonItem("Previous", UIBarButtonItemStyle.Bordered, PreviousField);
if (NextButtonVisible)
_NextButton = new UIBarButtonItem("Next", UIBarButtonItemStyle.Bordered, NextField);
UIBarButtonItem[] buttons = { _PrevButton, _NextButton };
return buttons.Union(baseButtons).Where((b)=>b != null).ToArray();
}