Hi @quoc, if you simply wish to get up and running using Eye Tracking in C#, then please follow the code snippet we provide @
As the Tobii.StreamEngine.Interop.cs is not a file that is to be ran directly as a sample application as the namespace ‘tobii_calibration_stimulus_points_t’ is only provided in conjunction with the purchase of an advanced use licence.
Please run the sample code we provide and let us know how you get on. Best Wishes.