Hi Rishi,
Thank you for your interest in Syncfusion Products.
The TabStripItem can be set defaultly selected through code behind using the below code snippet,
TabStrip1.Items[1].Selected = true;
Also please refer the below link for sample files which illustrates the above,
http://www.syncfusion.com/development/uploads/77000-Tabstrip_77609bf6.zipHope this helps you and please let me know if you have any other concerns.
Thanks,
Rekha