HomePage.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="MyAwesomeApp.HomePage"
             xmlns:viewModels="clr-namespace:MyAwesomeApp.ViewModels"
             x:DataType="viewModels:HomeViewModel">
    <ContentPage.BindingContext>
        <viewModels:HomeViewModel />
    </ContentPage.BindingContext>
    <ContentPage.Content>
        <StackLayout>
            <Entry Text="{Binding Greeting, Mode=TwoWay}" />
            <Label>
                <Label.FormattedText>
                    <FormattedString>
                        <Span Text="{Binding Greeting, Mode=OneWay}" />
                        <Span Text=", world!" />
                    </FormattedString>
                </Label.FormattedText>
            </Label>
        </StackLayout>
    </ContentPage.Content>
</ContentPage>