alignment problem

I have a stackLayout

        StackLayout sl1 = new StackLayout ();
        sl1.HorizontalOptions = LayoutOptions.FillAndExpand;
        sl1.Orientation = StackOrientation.Horizontal;

and two controls

        Label labelDataScadenza = new Label ();
        labelDataScadenza.Text = "Data scadenza:";

        DatePicker pickerDate = new DatePicker ();
        pickerDate.Format = "dd/MM/yyyy";

        sl1.Children.Add (labelDataScadenza);
        sl1.Children.Add (pickerDate);

Two controls are not aligned correctly. The second is lower than the first. It's a bug?