Hello Javad Habibi,
The CyUSB namespace has an event handler for attachment and detachment of USB device. The USBDeviceList.DeviceRemoved is an event handler for USB removal.
Please refer to the source code of Cypress USB Control Center, which can be found in the below path after the installation of CY3684 EZ-USB FX2LP Development Kit (Rev. *B) .
C:\Cypress\USB\CY3684\CY3684_EZ-USB_FX2LP_DVK\1.1\Windows Applications\Application Source files\c_sharp\controlcenter
This has got the implementation of event handling during the attachment and detachment of USB device.