Hi,
Thank you for your interest in Syncfusion Products.
I have tested the issue with the simple sample. I am afraid that I am not able to reproduce the issue. When I selected multiple treenodes and when I right click on it, I could see the context menu is displayed and also the multiple treenodes are still in selected state. Kindly refer to the sample provided below in which I have tested the issue.
http://files.syncfusion.com/support/Tools.Windows/7.1.0.30/F80669/main.htmPlease let me know if any concerns.
Regards,
Fathima