WPF _ PathListBox

<Grid x:Name="LayoutRoot" Background="White">
		<Path x:Name="path" Data="M437.5,210 C437.5,324.59909 340.12195,417.5 220,417.5 C99.878067,417.5 2.5,324.59909 2.5,210 C2.5,95.400917 99.878067,2.5 220,2.5 C340.12195,2.5 437.5,95.400917 437.5,210 z" Margin="100,30" Stretch="Fill" StrokeThickness="5">
			<Path.Stroke>
				<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
					<GradientStop Color="#FFA000FF" Offset="0"/>
					<GradientStop Color="Red" Offset="0.2"/>
					<GradientStop Color="#FFF1FF00" Offset="0.4"/>
					<GradientStop Color="#FF0004FF" Offset="0.6"/>
					<GradientStop Color="#FF08FF00" Offset="1"/>
					<GradientStop Color="#FFFFA400" Offset="0.8"/>
				</LinearGradientBrush>
			</Path.Stroke>
		</Path>
		<ec:PathListBox x:Name="pathListBox" HorizontalAlignment="Left" Height="100" 
						VerticalAlignment="Top" Width="100" FontSize="18.667" 
						FontWeight="Bold">
			<ec:PathListBox.LayoutPaths>
				<ec:LayoutPath SourceElement="{Binding ElementName=path}" Padding="35" Orientation="OrientToPath"/>
			</ec:PathListBox.LayoutPaths>
		</ec:PathListBox>
	</Grid>

This control is in the namespace http://schemas.microsoft.com/expression/2010/controls

In the code, add this one xmlns:ec="http://schemas.microsoft.com/expression/2010/controls"