i want when my window show, a RibbonTabItem (except first) activated.
How can do in xaml?
there is no IsActivated?
If you need to change the selected tab programatically you can also set the SelectedTab property of the xamRibbon. Again I would just reiterate that you should not do this to start the application with any tab but the first as that is required by the MS UI Guidelines/MS license to use the ribbon ui.
i found answer;
(from t in this.XamRibbon_Main.Tabs where (t.Header.ToString() == "BNPP") select t).First().IsSelected = true;
Whether you can or not, by using the ribbon you accept to follow Microsoft's Office UI Guidelines, which state that the "Home" tab (1) Must always be called "Home" (or the equivalent in another language) and (2) it must always be the selected tab when starting the application.
Here: http://msdn.microsoft.com/en-us/office/aa973809.aspx
can i do it in code?
No there is no such property because the Microsoft Office UI Guidelines require that the first tab be selected when the application is run.