<local:TestGrid>
            <Ellipse x:Name="CircleRed" Width="100" Height="100" Fill="Red" Stroke="Black" StrokeThickness="2"/>
        </local:TestGrid>

<UserControl x:Class="DiplomatCONTROLS.TestGrid"
    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"
    mc:Ignorable="d"
    d:DesignHeight="300" x:Name="dd" d:DesignWidth="400">
    <UserControl.Resources>
        <!-- A ContentControl template that defines your background -->
        <ControlTemplate x:Key="BackgroundTemplate" TargetType="ContentControl">
            <Grid>
                <Rectangle Fill="Beige" Stroke="Gray" StrokeThickness="1" Margin="10" RadiusX="15" RadiusY="10"/>
                <Rectangle Fill="White" Stroke="Gray" StrokeThickness="1" Margin="12,30,12,12" RadiusX="15" RadiusY="10"/>
                <Grid.Effect>
                    <DropShadowEffect BlurRadius="10" Direction="0" ShadowDepth="1"/>
                </Grid.Effect>
            </Grid>
        </ControlTemplate>
        <!-- A ContentControl Style that references the background template -->
        <Style x:Key="BackgroundStyle" TargetType="ContentControl">
            <Setter Property="Template" Value="{StaticResource BackgroundTemplate}" />
        </Style>
    </UserControl.Resources>
    <Canvas x:Name="LayoutRoot" Background="White">
        <Grid Width="300" Height="250">
            <ContentControl Style="{StaticResource BackgroundStyle}" />
            <!--<TextBlock Text="Your Cofent" Foreground="Red" FontSize="36" HorizontalAlignment="Center" VerticalAlignment="Center" />-->
        </Grid>
    </Canvas>
</UserControl>

<local:TestGrid/>

<local:TestGrid>
            <Ellipse x:Name="CircleRed" Width="100" Height="100" Fill="Red" Stroke="Black" StrokeThickness="2"/>
        </local:TestGrid>