WPF :Inheriting styles for third party controls

Question

Hi,

I am using telrik components for wpf. I want to get "Select all" Check Box on Grid Header cell

I have Common ResourceDictionary Style.Xaml , it has

<ResourceDictionary xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation"&gt;
    <Style TargetType="telerik:GridViewHeaderCell">
        <Setter Property="FontWeight" Value="ExtraLight" />
    </Style>
</ResourceDictionary>

Im MyWindow.Xaml I have

  <Window.Resources>
        <Style x:Key="CheckBoxHeaderCellStyle"  TargetType="telerik:GridViewHeaderCell">
            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="telerik:GridViewHeaderCell">
                        <CheckBox VerticalAlignment="Center"/>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </Window.Resources>

In code behind I am using

 var dict = new ResourceDictionary
                           {
                               Source = new Uri("MyApp;component/View/styles.xaml", UriKind.Relative)
                           };
Resources.MergedDictionaries.Add(dict);

I apply style in GridDataColumn as

<telerik:GridViewDataColumn HeaderCellStyle="{StaticResource CheckBoxHeaderCellStyle}"/>

In design mode I can see the checkbox in Grid Header.But It does not show a check box in GridHeader.