MainPage.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"
             xmlns:local="clr-namespace:ReactiveUIExampleXamarinForms"
             x:Class="ReactiveUIExampleXamarinForms.MainPage">

    <StackLayout Padding="12">
        <Label Text="Search:" VerticalOptions="Center" HorizontalOptions="Center" />
        <Entry x:Name="entryField" />
        <ActivityIndicator x:Name="loadingBar"/>
        <ListView x:Name="resultList"/>
    </StackLayout>

</ContentPage>