sa/Stars Assistant/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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:vm="using:StarsAssistant.ViewModels"
        xmlns:views="clr-namespace:StarsAssistant.Views"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="StarsAssistant.Views.MainWindow"
        x:DataType="vm:MainWindowViewModel"
        Icon="/Assets/avalonia-logo.ico"
        Title="GetStartedApp">

        <!-- Icon="/Assets/avalonia-logo.ico" -->

    <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>

    <TabControl>
        <TabItem Header="Stars Assistant">
            <Grid ColumnDefinitions="Auto, *" RowDefinitions="Auto, Auto">
                <Label Grid.Row="0" Grid.Column="0" Margin="0,5,5,5" Padding="3">Database Path:</Label>
                <TextBlock x:Name="DbPath" Grid.Row="0" Grid.Column="1" Margin="0 5" Padding="3"/>
            </Grid>
        </TabItem>
        <TabItem Header="BuCol">
            <views:BuColView x:Name="BuColView" 
                DataContext="{Binding BuColViewModel}" />
        </TabItem>
    </TabControl>
</Window>