presence_new/Presence.Desktop/Views/MainWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:app="clr-namespace:Presence.Desktop"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:vm="using:Presence.Desktop.ViewModels"
        xmlns:reactiveUi="http://reactiveui.net"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="Presence.Desktop.Views.MainWindow"
        x:DataType="vm:MainWindowViewModel"
		Title="MainWindow">
    <DockPanel>
        <reactiveUi:RoutedViewHost Router="{Binding Router}" DockPanel.Dock="Right" Background="AliceBlue">
            <reactiveUi:RoutedViewHost.ViewLocator>
                <app:ViewLocator/>
            </reactiveUi:RoutedViewHost.ViewLocator>
        </reactiveUi:RoutedViewHost>
    </DockPanel>
</Window>