[Mohamed El-Hamzawy]

Using RoboDk.Connect() in C# starts a new instance of robodk no matter what.

Expected Behavoiur:
When I do rdk.StartNewInstance = false;, It should not start a new instance.

[Albert]

RoboDK uses port 20500 by default to connect to the API. Did you change the port in RoboDK? (you can do so in Tools-Options-Other)

The API will try to connect to that port and if it is not available it will start a new instance. Optionally, you can specify a unique port to have a custom pair of API instance and RoboDK instance.