Hi Hongbin, thank you for the clarification, When I read your original post and with reference to the “C# Tobii Interaction API” I understood you meant our newer Interaction API Library offering that I had asked you to test.
Yes, The SDK you are currently using is referred to as the ‘Tobii Core SDK’. Unfortunately, you may have seen that this project is now deprecated and has not been updated since 2017. Accordingly, no resources are allocated for its maintenance and we now recommend all users migrate to the Interaction Library API.
A significant number of bugs and feature enhancements have gone into this newer Interaction Library API (including the bug you have already identified) so we must recommend therefore that you attempt to port the code across. Sorry that we did not clarify sooner, however this is the only course of action we can recommend for your situation. Thanks for your understanding.