CustomWindow in a CustomConrolLIb, only works on runtime

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custom-controls

Hell I have a created my own CustomWindow with a special design. I have a CustomControlLibrary. When I include it a
WPF Application and start the Application i see the new design. But I would like to see the new design in design time.

Here you will see my code of the CustomWindow

    public class CustomWindow : Window
    {
        static CustomWindow()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(CustomWindow), new FrameworkPropertyMetadata(typeof(CustomWindow)));
        }


        public void button1_Click(object sender, RoutedEventArgs e)
        {
            this.Close();
        }
    }


<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:cc ="clr-namespace:WpfCustomControlLibrary1"
    >
    <Style TargetType="{x:Type cc:CustomWindow}">
        <Setter Property="AllowsTransparency" Value="True"/>
        <Setter Property="WindowStyle" Value="None"/>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type cc:CustomWindow}">

                    <Border BorderBrush="Green" BorderThickness="1" CornerRadius="10" removed="Aquamarine">
                        <AdornerDecorator>
                            <ContentPresenter
                 ContentTemplate="{TemplateBinding ContentControl.ContentTemplate}"
                 Content="{TemplateBinding ContentControl.Content}" />
                        </AdornerDecorator>

                    </Border>
                    

                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

Here you will see my code of the Demo Application:

namespace WpfApplication1
{
    /// <summary>
    /// Interaktionslogik für MainWindow.xaml
    /// </summary>
    public partial class MainWindow : CustomWindow
    {
        public MainWindow()
        {
            InitializeComponent();
        }
    }

<my:CustomWindow x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:my="clr-namespace:WpfCustomControlLibrary1;assembly=WpfCustomControlLibrary1"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
        <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="74,84,0,0" Name="button1" VerticalAlignment="Top" Width="75" Click="button1_Click" />
    </Grid>
</my:CustomWindow>