How do I create a DropDown or Context Menu in WIndows Phone 8 using Xaml and C#?

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How to create DropDown or Context Menu in WIndows Phone 8 using Xaml and C#

hi i m beginner windows phone developer i wants to make context menu or drop down menu create using c# and xaml i have this code use given bellow but is it not working ....
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<TextBlock TextWrapping="Wrap" Text="Open Context Menu" Margin="98,218,129,441" FontSize="24">
<toolkit:ContextMenuService.ContextMenu>
<toolkit:ContextMenu Name="ctxMenuRoster">
<toolkit:MenuItem Header="option1" Click="MenuItem_Click"/>
<toolkit:MenuItem Header="option2" Click="MenuItem_Click_1"></toolkit:MenuItem>
</toolkit:ContextMenu>
</toolkit:ContextMenuService.ContextMenu>
</TextBlock>
</Grid>