Base para criar chat com template similar ao whatsApp

Chat.xaml

<ScrollView>
        <Grid RowSpacing="0" ColumnSpacing="0" >
            <Grid.RowDefinitions>
                <RowDefinition Height="*"/>
                <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>

            <ListView 
                x:Name="MessagesListView" 
                ItemTemplate="{StaticResource MessageTemplateSelector}" 
                ItemsSource="{Binding ListaChat}" 
                HasUnevenRows="True" SeparatorVisibility="None" IsEnabled="True" Grid.Row="0"/>


            <StackLayout Orientation="Horizontal" Grid.Row="1" BackgroundColor="White" VerticalOptions="EndAndExpand">
                <Entry 
                    HorizontalOptions="FillAndExpand"  
                    Placeholder="Messagem"  
                    Text="{Binding Mensagem}" Keyboard="Chat" Margin="4"/>
                <Image Source="ic_send_black_36dp.png" Margin="4">
                    <Image.GestureRecognizers>
                        <TapGestureRecognizer
                                Command="{Binding SendCommand}" />
                    </Image.GestureRecognizers>
                </Image>
            </StackLayout>

        </Grid>
    </ScrollView>

ChatViewModel.cs

public class ConsultaTabbedViewModel : BaseViewModel
	{
        public DelegateCommand SendCommand { get; set; }
        private ObservableCollection<Models.Entities.ChatMensagem> _listaChat;
        public ObservableCollection<Models.Entities.ChatMensagem> ListaChat
        {
            get { return _listaChat; }
            set { SetProperty(ref _listaChat, value); }
        }

        private string _mensagem;
        public string Mensagem
        {
            get { return _mensagem; }
            set { SetProperty(ref _mensagem, value); }
        }

        public ConsultaTabbedViewModel()
        {
            SendCommand = new DelegateCommand(ExecuteSendCommand);
            ListaChat = new ObservableCollection<Models.Entities.ChatMensagem>();
            AddChat();
        }

        private void ExecuteSendCommand()
        {
            if (!String.IsNullOrWhiteSpace(Mensagem))
            {
                var message = new Models.Entities.ChatMensagem
                {
                    Text = Mensagem,
                    IsTextIn = false, //Flag para indicar se a mensagem está sendo recebida (True) ou enviada (False).
                    MessageDateTime = DateTime.Now
                };


                ListaChat.Add(message);
                Mensagem = "";
            }
        }

        private void AddChat()
        {
            var lista = new ObservableCollection<Models.Entities.ChatMensagem>
            {
                new Models.Entities.ChatMensagem()
                {

                    BgColor = "#DCF8C6",
                    IsTextIn = false,
                    Text = "Mensagem 1"
                },
                new Models.Entities.ChatMensagem()
                {
                    BgColor = "#DCF8C6",
                    IsTextIn = false,
                    Text = "Mensagem 2"
                },
                new Models.Entities.ChatMensagem()
                {
                    BgColor = "#DCF8C6",
                    IsTextIn = false,
                    Text = "Mensagem 3"
                },
                new Models.Entities.ChatMensagem()
                {
                    Alinhamento = "Start",
                    BgColor = "White",
                    IsTextIn = true,
                    Text = "Mensagem 4"
                },
                new Models.Entities.ChatMensagem()
                {
                    BgColor = "White",
                    IsTextIn = true,
                    Text = "Mensagem 5"
                },
                new Models.Entities.ChatMensagem()
                {
                    BgColor = "#DCF8C6",
                    IsTextIn = false,
                    Text = "Mensagem 6"
                },
                new Models.Entities.ChatMensagem()
                {
                    BgColor = "White",
                    IsTextIn = true,
                    Text = "Mensagem 7"
                },
                new Models.Entities.ChatMensagem()
                {
                    IsTextIn = false,
                    BgColor = "#DCF8C6",
                    Text = "Mensagem 8"
                },
                new Models.Entities.ChatMensagem()
                {

                    IsTextIn = false,
                    BgColor = "#DCF8C6",
                    Text = "Mensagem 9"
                },
                new Models.Entities.ChatMensagem()
                {
                    IsTextIn = true,
                    BgColor = "White",
                    Text = "Mensagem 10"
                },
            };

            ListaChat = lista;
        }
    }

SelectorDataTemplate.cs

public class SelectorDataTemplate : DataTemplateSelector
    {
        private readonly DataTemplate textInDataTemplate;
        private readonly DataTemplate textOutDataTemplate;

        protected override DataTemplate OnSelectTemplate(object item, BindableObject container)
        {
            var messageVm = item as ChatMensagem;
            if (messageVm == null)
                return null;
            //Flag para indicar se a mensagem está sendo recebida (True) ou enviada (False).
            return messageVm.IsTextIn ? this.textInDataTemplate : this.textOutDataTemplate;
        }


        public SelectorDataTemplate()
        {
            this.textInDataTemplate = new DataTemplate(typeof(TextInViewCell));
            this.textOutDataTemplate = new DataTemplate(typeof(TextOutViewCell));
        }

    }

TextInViewCell.xaml

<?xml version="1.0" encoding="UTF-8"?>
<ViewCell xmlns="http://xamarin.com/schemas/2014/forms" 
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="DocHouse.CustomCells.TextInViewCell">
    <Grid ColumnSpacing="2" Padding="5">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="2"></ColumnDefinition>
            <ColumnDefinition Width="Auto"></ColumnDefinition>
            <ColumnDefinition Width="*"></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>
        </Grid.RowDefinitions>

        <Frame Grid.Row="0" Grid.Column="1" BackgroundColor="#0535f0" CornerRadius="15">
            <Frame.HasShadow>
                <OnPlatform x:TypeArguments="x:Boolean" iOS="false" Android="true"/>
            </Frame.HasShadow>
            <StackLayout>
                <Label TextColor="White" Text="{Binding Text}" />
            </StackLayout>
        </Frame>

        <Label FontSize="Micro" Grid.Row="1" Grid.Column="1" Text="{Binding MessageDateTime, StringFormat='{0:MM/dd/yyyy hh:mm tt}'}" TextColor="Gray"></Label>
    </Grid>
</ViewCell>

TextOutViewCell.xaml

<?xml version="1.0" encoding="UTF-8"?>
<ViewCell xmlns="http://xamarin.com/schemas/2014/forms" 
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="DocHouse.CustomCells.TextOutViewCell">
    <Grid ColumnSpacing="2" Padding="5">
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*"></ColumnDefinition>
            <ColumnDefinition Width="Auto"></ColumnDefinition>
            <ColumnDefinition Width="2"></ColumnDefinition>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"></RowDefinition>
            <RowDefinition Height="Auto"></RowDefinition>

        </Grid.RowDefinitions>

        <Frame Grid.Row="0"  Grid.Column="1" CornerRadius="15">
            <Frame.HasShadow>
                <OnPlatform x:TypeArguments="x:Boolean" Android="true" iOS="false"/>
            </Frame.HasShadow>
            <Frame.BackgroundColor>
                <OnPlatform x:TypeArguments="Color" Android="White" iOS="#F5F5F5"/>
            </Frame.BackgroundColor>

            <StackLayout>
                <Label TextColor="Black"  Text="{Binding Text}" />
            </StackLayout>
        </Frame>
        <Label Grid.Row="1" FontSize="Micro" Grid.Column="1" HorizontalTextAlignment="End"  Text="{Binding MessageDateTime, StringFormat='{0:MM/dd/yyyy hh:mm tt}'}" TextColor="Gray"></Label>

    </Grid>
</ViewCell>