Nullability of type of parameter 'obj' doesn't match overridden member (possibly because of nullability attributes).

Cannot convert null literal to non-nullable reference type.

Converting null literal or possible null value to non-nullable type.

Dereference of a possibly null reference.

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

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

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

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

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