Hi Sia,
I looked briefly in your sample code. It looks like one problem is the using statements:
using (var eyeXHost = new EyeXHost())
{
eyeXHost.Start();
using (var stream = eyeXHost.CreateGazePointDataStream(GazePointDataMode.LightlyFiltered))
{
// ...
This means that the EyeXHost and data stream instances will be disposed right afterwards. You need to save a reference to the EyeXHost and stream object, and only dispose them when you dispose your TobiiController instance.
See MSDN for best practices regarding the using statement and IDisposable:
http://msdn.microsoft.com/en-us/library/fs2xkftw.aspx
http://msdn.microsoft.com/en-us/library/yh598w02.aspx