Hi Subarta,
Thank you for your interest in Syncfusion Products.
I am afraid that I am not able to reproduce the issue. I tested the sample in which I programmatically select an item when the ComboBox DropDown button is clicked. When I traverse the items using up arrow key I am able to select the previous items. Please refer to the sample provided below that illustrates this:
http://files.syncfusion.com/support/Tools.Windows/7.2.0.20/F80986/main.htmIf I have misunderstood your requirement, could you please let me know in detail so that I could work out in depth and provide you a better solution at the earliest?
Please let me know if any concerns.
Regards,
Fathima