HKCard/HKCardOUT/Views/RootView.xaml

<hc:Window x:Class="HKCardOUT.Views.RootView"
           xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
           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:viewModels="clr-namespace:HKCardOUT.ViewModels"
           xmlns:hc="https://handyorg.github.io/handycontrol"
           mc:Ignorable="d"
           d:DataContext="{d:DesignInstance Type=viewModels:RootViewModel}"
           Title="{Binding Title}" 
           WindowStartupLocation="CenterScreen"
           ShowTitle="True"
           Height="450" 
           Width="800">
    <TextBlock Text="Hello World" HorizontalAlignment="Center" VerticalAlignment="Center" />
</hc:Window>