C# 'ResourceDictionaryCollection' does not exist

I am Getting Error如下所示:

  Error 1   The tag 'ResourceDictionaryCollection' does not exist in XML
     namespace 'clr-namespace:System.Windows.Controls.DataVisualization;
    assembly=System.Windows.Controls.DataVisualization.Toolkit'.

代码如下:

             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             xmlns:DV="clr-namespace:System.Windows.Controls.DataVisualization;assembly=System.Windows.Controls.DataVisualization.Toolkit"
             xmlns:DVC="clr-namespace:System.Windows.Controls.DataVisualization.Charting;assembly=System.Windows.Controls.DataVisualization.Toolkit"
             mc:Ignorable="d" 
             MinHeight="384" MinWidth="579">
    <UserControl.Resources>
        <DV:ResourceDictionaryCollection x:Key="MyPalette">
            <ResourceDictionary>
                <Style x:Key="DataPointStyle" TargetType="Control">
                    <Setter Property="Background" Value="Purple" />
                </Style>
            </ResourceDictionary>

我应该如何纠正这个错误?我在Visual c# 2010上运行。我已经安装了WPF工具包，但我仍然得到命名空间错误。