Hi Patrick,
Thanks for using Syncfusion Products.
If your intention is to select the tab in Ribbon control means please use CheckState property in ToolStripTabItem .
The following code snippet which illustrates how to select the tab in ribbon control.
toolStripTabItem2.CheckState = CheckState.Checked;
Please refer to the attached sample from the following page
http://websamples.syncfusion.com/samples/Diagram.Windows/36464/main.htmPlease let me know if you have any more queries.
Regards,
Nagaraj