Example of how to use framework de Machine Learning ML.NET in your Xamarin.Forms applications - http://julianocustodio.com/utilizando-ml-net-em-aplicacoes-xamarin-forms

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:DemoCommentary" 
             x:Class="DemoCommentary.MainPage">
    <StackLayout Margin="20">
        <Entry Placeholder="Texto" x:Name="Texto"/>
        <Button Text="Resultado" Clicked="GetResult"/>
        <Image x:Name="Emoji" WidthRequest="60" HorizontalOptions="Center"/>
        <Label x:Name="LblResult" HorizontalOptions="Center"/>
    </StackLayout>
</ContentPage>