Error while drawing pie chart

[ERUM]

<UserControl x:Class="ChartApplication.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:DV="clr-namespace:System.Windows.Controls.DataVisualization;assembly=System.Windows.Controls.DataVisualizati on"
xmlns:DVC="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVi sualization"

xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480">

<Grid x:Name="LayoutRoot">
<DVC:Chart x:Name="MyChart" Width="400" Height="250"

Background="YellowGreen">

</DVC:Chart>




</Grid>
</UserControl>


i have above code in silver light applciation and added reference too for charting etc etc too
but it gives me an error
Error 1 The tag 'Chart' does not exist in XML namespace 'clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVi sualization'. C:\Users\Iram\Documents\Visual Studio 2008\Projects\ChartApplication\ChartApplication\ChartApplication\MainPage.xaml 12 10 ChartApplication


Thanks