Thingsboard.NET is a .NET client library for Thingsboard IoT Platform. It is a .NET Standard 2.0 library, so it can be used in .NET Core and .NET Framework applications.
i've testing around with your project. I stumbled only about one issue. I could not save a device with additionalInfos.
I think there is no way i could add following to the save process. "additionalInfo": { "gateway": true }
In the thingsboard api docu its and the end of the example thinkboardLink