class WindowEx : public NoesisApp::Window {}
class SingleModeWindow : public WindowEx {}

<!--  WindowEx  -->
<ControlTemplate x:Key="Template.WindowEx" TargetType="{x:Type WindowEx}">
   <Grid x:Name="Grid.Main" Margin="2">
            .... 
    <ContentPresenter Margin="0" />       
  </Grid>
</ControlTemplate>
 
 <Style x:Key="Style.WindowEx" TargetType="{x:Type WindowEx}">
    <Setter Property="OverridesDefaultStyle" Value="True" />
    <Setter Property="Template" Value="{StaticResource Template.WindowEx}" />
</Style>

<WindowEx
    x:Class="SingleModeWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:b="http://schemas.microsoft.com/xaml/behaviors"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:ei="http://schemas.microsoft.com/expression/2010/interactions"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:noesis="clr-namespace:NoesisGUIExtensions"
    WindowStyle="None"
    ShowInTaskbar="True"
    Style="{StaticResource Style.WindowEx}"
    mc:Ignorable="d">
	<Grid x:Name="#ContentGrid#"></Grid>	
</WindowEx>