Observer pattern among two ViewModels using Avalonia and ReactiveUI frameworks

MainWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="using:AvaloniaObserver.ViewModels"
        xmlns:views="using:AvaloniaObserver.Views"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="AvaloniaObserver.Views.MainWindow"
        x:DataType="vm:MainWindowViewModel"
        Icon="/Assets/avalonia-logo.ico"
        Title="AvaloniaObserver">

    <Design.DataContext>
        <!-- This only sets the DataContext for the previewer in an IDE,
             to set the actual DataContext for runtime, set the DataContext property in code (look at App.axaml.cs) -->
        <vm:MainWindowViewModel/>
    </Design.DataContext>

    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center" >
        <ContentControl Content="{Binding PublisherControl}"/>
        <ContentControl VerticalAlignment="Top" Content="{Binding SubscriberControl}"/>
    </StackPanel>

</Window>

MainWindowViewModel.cs

using ReactiveUI;
using System;
using System.Windows.Input;
using System.Reactive;
using System.Reactive.Linq;

namespace AvaloniaObserver.ViewModels;

public partial class MainWindowViewModel : ViewModelBase
{
    public PublisherControlViewModel PublisherControl { get; }
    public SubscriberControlViewModel SubscriberControl { get; }

    
    public MainWindowViewModel()
    {
        PublisherControl = new PublisherControlViewModel();
        SubscriberControl = new SubscriberControlViewModel(PublisherControl.SubmitTextCommand);
    }
}

PublisherControlView.axaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:vm="using:AvaloniaObserver.ViewModels"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
             x:DataType="vm:PublisherControlViewModel"
             x:Class="AvaloniaObserver.Views.PublisherControlView">

    <Design.DataContext>
        <vm:PublisherControlViewModel/>
    </Design.DataContext>

    <StackPanel Spacing="10" Margin="20" VerticalAlignment="Center">
        <TextBox Watermark="Insert text here..."
                 Text="{Binding InputText}"
                 Name="InputText"
                 Height="200"
                 Width="400"
                 AcceptsReturn="True"
                 TextWrapping="Wrap" />
        <Button Content="Conferma" HorizontalAlignment="Center" Command="{Binding SubmitTextCommand}" />
    </StackPanel>

</UserControl>

PublisherControlViewModel.cs

using System;
using System.Reactive.Linq;
using System.Reactive;
using ReactiveUI;

namespace AvaloniaObserver.ViewModels;

public partial class PublisherControlViewModel : ViewModelBase
{
    // InputTextConent property will contain the wrote message
    private string _InputTextValue;
    public string InputText
    {
        get => _InputTextValue;
        set => this.RaiseAndSetIfChanged(ref _InputTextValue, value);
    }

    // With the SubmitTextCommand the observer will be notified regarding the text submission
    public ReactiveCommand<Unit, string> SubmitTextCommand { get; }


    public PublisherControlViewModel()
    {
        _InputTextValue = string.Empty;
        SubmitTextCommand = ReactiveCommand.Create(SubmitText, this.WhenAnyValue(x => x.InputText, data => !string.IsNullOrEmpty(data)));
    }
    
    public string SubmitText()
    {
        return InputText;
    }
}

SubscriberControlView.axaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:vm="using:AvaloniaObserver.ViewModels"
             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
             x:DataType="vm:SubscriberControlViewModel"
             x:Class="AvaloniaObserver.Views.SubscriberControlView">
    
    <StackPanel Spacing="10" Margin="20" VerticalAlignment="Center">
        <TextBox Watermark="Text will be displayed here..."
                 Text="{Binding ReversedText}"
                 Name="ReversedText"
                 Height="200"
                 Width="400"
                 AcceptsReturn="True"
                 TextWrapping="Wrap"
                 IsReadOnly="True" />
    </StackPanel>

</UserControl>

SubscriberControlViewModel.cs

using System;
using System.Windows.Input;
using System.Reactive.Linq;
using System.Reactive;
using ReactiveUI;

namespace AvaloniaObserver.ViewModels;

public partial class SubscriberControlViewModel : ViewModelBase
{
    private string _ReversedTextValue;
    public string ReversedText
    {
        get => _ReversedTextValue;
        set => this.RaiseAndSetIfChanged(ref _ReversedTextValue, value);
    }


    public SubscriberControlViewModel(ReactiveCommand<Unit, string> extCommand)
    {
        _ReversedTextValue = string.Empty;
        extCommand
            .Subscribe(data =>
            {
                UpdateText(data);
            });
    }


    public void UpdateText(string data)
    {
        char[] dataArray = data.ToCharArray();
        Array.Reverse(dataArray);
        ReversedText = new string(dataArray);
    }
}