crosslangdevstudio/Views/MainWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:vm="using:CrossLangDevStudio.ViewModels"
        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="CrossLangDevStudio.Views.MainWindow"
        x:DataType="vm:MainWindowViewModel"
        Icon="/Assets/crosslang.ico"
        Title="CrossLang DevStudio"
        xmlns:controls="clr-namespace:Tabalonia.Controls;assembly=Tabalonia">

    <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>


     <Grid>
          <Grid.RowDefinitions>
             <RowDefinition Height="Auto" />
             <RowDefinition Height="*" />
          </Grid.RowDefinitions>
          <Menu Grid.Row="0">
      <MenuItem Header="_File">
        <MenuItem Header="_New Project" HotKey="Ctrl+N" Command="{Binding NewProjectCommand}"/>
        <MenuItem Header="_Open Project" HotKey="Ctrl+O" Command="{Binding OpenProjectCommand}"/>
        <MenuItem Header="_Save" HotKey="Ctrl+S" Command="{Binding SaveCommand}"/>
        <MenuItem Header="Save All" HotKey="Ctrl+Shift+S" Command="{Binding SaveAllCommand}"/>
        <Separator/>
        <MenuItem Header="_Exit" HotKey="Alt+F4"/>
      </MenuItem>
      <MenuItem Header="_Project">
        <MenuItem Header="Build" Command="{Binding BuildCommand}" />
        <MenuItem Header="Build And Run" HotKey="F5" Command="{Binding BuildAndRunCommand}" />
        <MenuItem Header="Publish" Command="{Binding PublishCommand}" />
        <MenuItem Header="Open In File Manager" Command="{Binding OpenProjectInFileManagerCommand}" />
        <MenuItem Header="Open In Terminal" HotKey="CTRL+T" Command="{Binding OpenProjectInTerminalCommand}" />
        <MenuItem Header="Refresh" HotKey="CTRL+R" Command="{Binding RefreshListingCommand}" />
      </MenuItem>
      <MenuItem Header="_CPKG">
        <MenuItem Header="Add Package" Command="{Binding AddPackageCommand}"/>
        <MenuItem Header="Install">
            <MenuItem Header="Template" Command="{Binding InstallTemplateCommand}"/>
            <MenuItem Header="Tool" Command="{Binding InstallToolCommand}"/>
            <MenuItem Header="Web Application" Command="{Binding InstallWebAppCommand}"/>
            <MenuItem Header="Console Application" Command="{Binding InstallConsoleCommand}"/>
        </MenuItem>
        <MenuItem Header="Push Package" Command="{Binding PushPackageCommand}"/>
      </MenuItem>
      <MenuItem Header="_Help">     
          
        <MenuItem Header="Welcome" Command="{Binding WelcomeCommand}"/>  
        <MenuItem Header="Website" Command="{Binding WebsiteCommand}"/>
        <MenuItem Header="Documentation" Command="{Binding DocumentationCommand}"/>
        <MenuItem Header="Video Documentation" Command="{Binding VideoDocumentationCommand}" />
        <MenuItem Header="Reference" Command="{Binding ReferenceCommand}" />
      </MenuItem>
    </Menu>
     <Grid Grid.Row="1" ColumnDefinitions="300, 4, *">
        <TreeView Grid.Column="0" ItemsSource="{Binding ProjectFiles}" SelectedItem="{Binding SelectedProjectFile}">
            <!--Thanks to https://stackoverflow.com/a/77362693 -->
            <TreeView.ItemContainerTheme>
                <ControlTheme TargetType="TreeViewItem" BasedOn="{StaticResource {x:Type TreeViewItem}}">
                    <Setter Property="IsExpanded" Value="True" />
                </ControlTheme>
            </TreeView.ItemContainerTheme>
            <TreeView.ItemTemplate>
                <TreeDataTemplate ItemsSource="{Binding SubNodes}">
                    <TextBlock Text="{Binding Title}"/>
                </TreeDataTemplate>

            </TreeView.ItemTemplate>
        </TreeView>
    
    <GridSplitter Grid.Column="1" Background="Black" ResizeDirection="Columns"/>

    <controls:TabsControl SelectedItem="{Binding SelectedTab}" Grid.Column="2" ItemsSource="{Binding TabItems}"
                          NewItemFactory="{Binding NewItemFactory}"
                          LastTabClosedAction="{Binding Closed}"
                          TabClosing="{Binding ClosingTab}"
                          ShowDefaultAddButton="True"
                          ShowDefaultCloseButton="True"
                          Margin="0 8 0 0"
                          HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
        <TabControl.ContentTemplate>
            <DataTemplate DataType="vm:TabItemViewModel">

                <Grid Background="{DynamicResource SelectedTabItemBackgroundBrush}">
                    <TransitioningContentControl Content="{Binding Body}" Grid.Column="2"/>
                </Grid>

            </DataTemplate>
        </TabControl.ContentTemplate>

        <TabControl.ItemTemplate>
            <DataTemplate DataType="vm:TabItemViewModel">
                <TextBlock Text="{Binding Header}" />
            </DataTemplate>
        </TabControl.ItemTemplate>
        
    </controls:TabsControl>
    </Grid>
    </Grid>
</Window>