Virtual COM port driver receive interrupt

Hi Guys,
I am modifying the fakemodem driver for creating Virutal serial port given in driver samples,
I am opening the port in Windows Forms application and reading and writing data to it.
But data received event in the Forms application doesnt fire. I can see that data is being reflected in the readBuffer and the number of bytes available to read option, But the dataReceivedEvent doesnt fire.
The fakemodem driver doesnt have the Driverextension structure as in the serial driver sample. Is it necessary to include the driver extension structure?
What is the mechanism that makes the dataReceivedEvent fire? Please help.