Nullability of reference types in type of 'event PropertyChangedEventHandler WorldAnalyzerPage.PropertyChanged' doesn't match implicitly implemented member 'event PropertyChangedEventHandler? INotifyPropertyChanged.PropertyChanged'.

Nullability of reference types in type of parameter 'other' of 'int TreeListClass.CompareTo(TreeListClass other)' doesn't match implicitly implemented member 'int IComparable<TreeListClass>.CompareTo(TreeListClass? other)' (possibly because of nullability attributes).

Nullability of reference types in type of 'event PropertyChangedEventHandler TreeListClass.PropertyChanged' doesn't match implicitly implemented member 'event PropertyChangedEventHandler? INotifyPropertyChanged.PropertyChanged'.

Cannot convert null literal to non-nullable reference type.

Possible null reference return.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Dereference of a possibly null reference.

Dereference of a possibly null reference.