ChatPage.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="ChatUIXForms.Views.ChatPage" 
             xmlns:local="clr-namespace:ChatUIXForms.Helpers" 
             xmlns:partials="clr-namespace:ChatUIXForms.Views.Partials">
    <ContentPage.Resources>
        <ResourceDictionary>
            <local:ChatTemplateSelector x:Key="MessageTemplateSelector"/>
        </ResourceDictionary>
    </ContentPage.Resources>
     <Grid RowSpacing="0" 
           ColumnSpacing="0">
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="1" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>
        <ListView Grid.Row="0" 
                 ItemTemplate="{StaticResource MessageTemplateSelector}" 
                 ItemsSource="{Binding Messages}" 
                 Margin="0" 
                 HasUnevenRows="True" 
                 VerticalOptions="FillAndExpand" 
                 SeparatorColor="Transparent" >
        </ListView>
        <BoxView HorizontalOptions="FillAndExpand"
                 HeightRequest="1"
                 BackgroundColor="LightGray"
                 Grid.Row="1"/>
        <partials:ChatInputBarView Grid.Row="2"
                                   Margin="0,0,10,0"/>
    </Grid>
</ContentPage>