Nullability of reference types in type of parameter 'state' of 'void UdpTimedSender.SendMessageCallback(object state)' doesn't match the target delegate 'TimerCallback' (possibly because of nullability attributes).

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

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

Cannot convert null literal to non-nullable reference type.

Possible null reference return.

The variable 'ex' is declared but never used

The variable 'ex' is declared but never used

Cannot convert null literal to non-nullable reference type.

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