This example show how to building a Xamarin.Forms applications using Microsoft Cognitive Services to identify if two pictures are from same person - http://julianocustodio.com/face-verify

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:DemoFaceVerify"
             x:Class="DemoFaceVerify.MainPage">

    <StackLayout>
        <StackLayout Orientation="Horizontal" 
                     HorizontalOptions="Center" 
                     VerticalOptions="Center" BackgroundColor="DarkSlateGray">
            <Image x:Name="MinhaImagem1" Aspect="AspectFill" HeightRequest="200" 
                   WidthRequest="400" HorizontalOptions="CenterAndExpand" />
        </StackLayout>
        <Button Text="Tirar Foto 1" Clicked="TakePicture1" FontSize="20" />

        <StackLayout Orientation="Horizontal" 
                     HorizontalOptions="Center" 
                     VerticalOptions="Center" BackgroundColor="DarkSlateGray">
            <Image x:Name="MinhaImagem2" Aspect="AspectFill" HeightRequest="200" 
                   WidthRequest="400" HorizontalOptions="CenterAndExpand" />
        </StackLayout>
        <Button Text="Tirar Foto 2" Clicked="TakePicture2" FontSize="20" />

        <Button Text="Verificar" Clicked="FaceVerify" BackgroundColor="Blue"/>
    </StackLayout>

</ContentPage>