Silverlight 4: ContentTemplate Background Change - silverlight

Question

I have a Header style for my datagrid custom header. I am using theme for my application. The problem here is the header background of the datagrid is not changing however when I remove the styles, the header background has no problem, it change.
Here's the themes
Here's my sample application, right click the grid and context menu will appear for the list of themes, select the different themes. I have two columns namely, with header style and without header style. See the difference. Thank you for your help.
<Style x:Key="DataGridHeaderStyle" TargetType="primitive:DataGridColumnHeader">
<Setter Property="HorizontalContentAlignment" Value="Stretch" />
<Setter Property="ContentTemplate">
<Setter.Value>
<DataTemplate>
<Grid HorizontalAlignment="Stretch">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<TextBlock Text="{Binding}" Grid.Column="0" HorizontalAlignment="Left" />
<filter:DataGridColumnFilter Grid.Column="1" HorizontalAlignment="Right" />
</Grid>
</DataTemplate>
</Setter.Value>
</Setter>
</Style>
Thank you

Answer 1

I did a quick test, and it does not seem to work with either the tag approach or the ImplicitStyleManager attribute approach. This is probably because the style setter is outside the scope and therefore gets applied without a theme.
Suggestion 1: Look at the way that the Jet Pack theme handles it with resource dictionaries in App.xaml, and try to do something similar. (You will need the theme.xaml file for this. EDIT: This link might help.) If you want to change the theme dynamically, then consider this (old) post about swapping themes in resource dictionaries (I haven't tried it, but it should work).
Suggestion 2: You need to think about style inheritance. Since "BasedOn" needs an x:Key tag, you could instead copy the theme's implicit DataGridColumnHeader style and only modify the parts you are interested in. (I don't know if there's a more elegant way.)
If this is not what you meant, then please provide more sample code.
EDIT [2010-12-09]:
I looked at the code, and I believe the root of the problem is the absence of style inheritance. Your "DataGridHeaderStyle" is saying "Do not use the normal DataGridColumnHeader style, but instead use this TextBlock inside this Grid." So Silverlight does just that: it gives you a styled TextBlock in an unstyled default DataGridColumnHeader.
Proof: Update your "Home.xaml" and add a TextBox in the second column of your "DataGridHeaderStyle" style, next to the current TextBlock. Notice how the theme for the TextBox in the header is changing every time you change the theme (look at the TextBox backgroud), but the background of the column header is stuck on the default colour. Like I said, your custom style is telling Silverlight to ignore the implicit style.
FIX: I do not know how to inherit from implicit styles without an "x:Key" attribute. I googled quite a bit but could not find anything helpful. You will either have to a) create a custom column definition style for all your datagrid headers, or you will have to b) bother the Silverlight team for a new feature in the next version of Silverlight. Or c) pick one theme to stick with and edit a copy of the theme's implicit column header style as your new "DataGridHeaderStyle" style.
My holiday is about to start, so I hope this helped. At least now you know where the problem lies.