UISegmentedControl:当在工具栏中使用时不触发事件

Monotouch 4.2 beta版

我把一个UISegmentedControl加到一个UIToolbar。问题是在切换段时没有触发任何事件。我遗漏了什么?

this.oBookmarkSwitch = new UISegmentedControl(new UIImage[] { UIImage.FromFile("./images/index.png"), UIImage.FromFile("./images/bookmark_grey.png") });
this.oBookmarkSwitch.TouchUpInside += delegate {
Console.WriteLine("TOUCHY - never fires");
};
this.oBookmarkSwitch.ValueChanged += delegate {
Console.WriteLine("CHANGE - only fires once when the control is created");
};
this.oBookmarkSwitch.Frame = new RectangleF(0, 0, 100, 30);
this.oBookmarkSwitch.ControlStyle = UISegmentedControlStyle.Bar;
aBarButtons.Add(new UIBarButtonItem(this.oBookmarkSwitch));
oIndexToolbar.SetItems (aBarButtons.ToArray (), false);