Possible null reference assignment.

Non-nullable property 'TestString' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

This async method lacks 'await' operators and will run synchronously. Consider using the 'await' operator to await non-blocking API calls, or 'await Task.Run(...)' to do CPU-bound work on a background thread.

Possible null reference assignment.

Non-nullable property 'TestString' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.