How to get the GUID of usb device such as mp3 or a simple flash memory

Question

I want to retrieve the DeviceID of usb device, i m using some functions from Windows API like SetupDiGetClassDev(), the problem is how to obtain the GUID for that kind of devices they are not HID device type and then pass to SetupDiGetClassDev that GUID.

Could you give me, please, an example in C#, Or just tell me how can i do that?
very thanks in advance, and sorry my english, is not my native languaje