Hi Cheng,
the data streams framework has been evolving a bit in the latest SDK releases. We’re sorry for the trouble that’s causing, but we believe it’s best for the API in the long run. The good news is that the sample applications have been evolving too: there are samples called MinimalGazeDataStream both in the C/C++ SDK package and in the .NET SDK package that use a lightly filtered gaze data stream.
I’d also recommend browsing though the release notes in the Readme file in the SDK package when upgrading.