Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Possible null reference argument for parameter 'learningContent' in 'LearningElementPe.LearningElementPe(string name, ILearningContentPe learningContent, string description, string goals, LearningElementDifficultyEnum difficulty, ElementModel elementModel, int workload = 0, int points = 1, double positionX = 0, double positionY = 0)'.

'MockedRequestExtensions.Respond(MockedRequest, HttpResponseMessage)' is obsolete: 'Using this overload is not recommended. Instead, use Respond(req => new HttpResponseMessage(...))'

'MockedRequestExtensions.Respond(MockedRequest, HttpResponseMessage)' is obsolete: 'Using this overload is not recommended. Instead, use Respond(req => new HttpResponseMessage(...))'

Non-nullable field '_fileSystem' must contain a non-null value when exiting constructor. Consider declaring the field 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.

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.

Dereference of a possibly null reference.