How to pass a structture to a driver using Deviceiocontrol

Hi all,
I want to pass a structure from my application written in C# to a
wince stream interface driver(written as a service) using
deviceiocontrol method.
The code to handle the device iocontrol code is implemented in
XXX_iocontrol function of the driver.But I am getting a compilation
error stating that the custom IOCTL code that i have defined is not a
valid label.
I have defined my ioctl code in the stream driver's