Ooui-tws-port/Samples/ButtonXamlPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="ButtonXaml.ButtonXamlPage">

    <StackLayout Padding="20">
        <Label Text="Welcome to Xamarin.Forms!"/>
        <Label x:Name="LabelCount" Text="Click Count: 0"/>
        <Button Text="Tap for click count!"
                Clicked="OnButtonClicked" />
    </StackLayout>
</ContentPage>