DEMOUP/DemoPractick/Add.xaml

<Window x:Class="DemoPractick.Add"
        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:local="clr-namespace:DemoPractick"
        mc:Ignorable="d"
        Title="Add" Height="450" Width="800">
    <Grid>
        <StackPanel Orientation="Vertical">
            <TextBox Text="{Binding Path=GetSelectedProduct.ArticleNumber}"/>
            <TextBlock Text="{Binding Path=Title}"></TextBlock>
            <TextBlock Text="{Binding Path=Count}" ></TextBlock>
            <TextBlock></TextBlock>
            <TextBlock></TextBlock>

        </StackPanel>
    </Grid>
</Window>