http://es.infragistics.com/community/blogs/andrew_smith/archive/2009/12/09/common-style-issues-when-using-the-theme-property.aspx

And this xaml will accomplish what you are looking for.

<igWindows:XamTabControl Name="xamTabCtrl" DataContext="{Binding }"      

ItemsSource="{Binding }"             

Theme="Metro"   > 

<igWindows:XamTabControl.Resources>

<Style TargetType="igWindows:TabItemEx"

BasedOn="{x:Static igThemes:PrimitivesMetro.TabItemEx}">

<Setter Property="Header" Value="{Binding Path=Header}" />

</Style>

</igWindows:XamTabControl.Resources>         

<igWindows:XamTabControl.ContentTemplate>

<DataTemplate>

<igDP:XamDataGrid Theme="Metro" 

DataSource="{Binding Logins}"/>

</DataTemplate>

</igWindows:XamTabControl.ContentTemplate>

</igWindows:XamTabControl> 

Hope this helps you.  Please let me know if you have any questions. 

Hi,

I'm looking into your stackoverflow question and I'll try to answer it here shortly.

I appreciate your patience while I look into this further.