New Post: De.TorstenMandelkow.MetroChart.dll WPF Error

When I Use This Dll On My Appication Like......................
<MetroChart:PieChart HorizontalAlignment="Left" Margin="31,16,0,0" x:Name="PieChart" SelectedItem="{Binding Path=SelectedItem,Mode=TwoWay}" VerticalAlignment="Top" Height="365" Width="647" RenderTransformOrigin="0.5,0.5">

<MetroChart:PieChart.Series>
            <MetroChart:ChartSeries DisplayMember="Display" ToolTip="Uday" ValueMember="Value" ItemsSource="{Binding Path=Errors}"/>

        </MetroChart:PieChart.Series>

    </MetroChart:PieChart>

Then This Show Error

The tag 'PieChart' does not exist in XML namespace 'clr-namespace:De.TorstenMandelkow.MetroChart;assembly=De.TorstenMandelkow.MetroChart'.

How To Solve This Error ?