Thank you for contacting us.
I am not sure what you mean by searching through multiple columns in a combo box but in our Q3 2012 release of RadControls we introduced a new RadAutoCompleteBox
control which has a built-in filtering, virtualization and auto complete functionality that could be useful in your scenario. You can see our demos for RadAutoCompleteBox here
and our online documentation here
It is worth mentioning that it is possible to customize the filtering feature of the control and change the way items are filtered.
If you have any other questions feel free to write to us again.
the Telerik team