Well, of course the .NET environment does include functionality to control the cursor icon. You can find it by searching the Internet, e.g., for something like ".net cursor icon":
However, that sounds like treatment of the symptom instead of addressing the cause. I suggest that you analyse your add-in more carefully to find out what is causing this symptom in the first place. For instance, you could comment out all of your code, verify that the cursor remains in its intended state, and then uncomment bit and pieces step by step to discover what section is causing the problem. Then you can treat and fix the root cause.