Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Nullability of reference types in type of parameter 'x' of 'int DeviceComparer.Compare(object x, object y)' doesn't match implicitly implemented member 'int IComparer.Compare(object? x, object? y)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'y' of 'int DeviceComparer.Compare(object x, object y)' doesn't match implicitly implemented member 'int IComparer.Compare(object? x, object? y)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'x' of 'int ScreenComparer.Compare(object x, object y)' doesn't match implicitly implemented member 'int IComparer.Compare(object? x, object? y)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'y' of 'int ScreenComparer.Compare(object x, object y)' doesn't match implicitly implemented member 'int IComparer.Compare(object? x, object? y)' (possibly because of nullability attributes).

The variable 'result' is declared but never used

Nullability of reference types in type of parameter 'sender' of 'anonymous method' doesn't match the target delegate 'EventHandler<KeyPressedEventArgs>' (possibly because of nullability attributes).

Non-nullable event 'KeyPressed' must contain a non-null value when exiting constructor. Consider declaring the event as nullable.