<Style TargetType="Window">
        <Setter Property="SnapsToDevicePixels" Value="True"/>
        <Setter Property="Background" Value="DarkGray"/>
        <Setter Property="Title" Value="My custom window"/>
        <Setter Property="WindowChrome.WindowChrome">
            <Setter.Value>
                <WindowChrome ResizeBorderThickness="5" CaptionHeight="30" GlassFrameThickness="0" CornerRadius="0"/>
            </Setter.Value>
        </Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="Window">
                    <Border BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}">
                        <Grid Background="Transparent">

                            <!-- Title bar -->
                            <Border Background="White" Height="30" VerticalAlignment="Top">
                                <Grid>
                                    <!-- Window title -->
                                    <TextBlock Text="{TemplateBinding Title}" HorizontalAlignment="Left" VerticalAlignment="Center" Margin="10,0,0,0"/>

                                    <!-- Window control buttons stack -->
                                    <StackPanel HorizontalAlignment="Right">
                                        <!-- Close button, for example -->
                                        <Button Width="40" Height="30" Background="White" WindowChrome.IsHitTestVisibleInChrome="True" Click="Button_Click">
                                            <Path Data="M0,0 L20,20 M0,20 L20,0" Stroke="Black" StrokeThickness="1"/>
                                        </Button>
                                    </StackPanel>
                                </Grid>
                            </Border>

                            <!-- Window content -->
                            <AdornerDecorator>
                                <ContentPresenter Margin="0,30,0,0"/>
                            </AdornerDecorator>
                        </Grid>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>

</Window.Style>