ItemSelected and ItemTapped events not firing in a Xamarin.Forms solution

public class SubMenuCell:ViewCell
{
public SubMenuCell()
{
this.Tapped += SubMenuCell_Tapped;
View = new StackLayout
{
Children =
{
new Label{Text="Description"},
new Button{Text="Button"}
}
};

        void SubMenuCell_Tapped(object sender, EventArgs e)
        {
        }

}

If the viewCell contains a Button control then ViewCell Tapped the event does not fire.
thank you