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

Cannot convert null literal to non-nullable reference type.

Nullability of reference types in type of parameter 'x' of 'bool FilePathComparer.Equals(string x, string y)' doesn't match implicitly implemented member 'bool IEqualityComparer<string>.Equals(string? x, string? y)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'y' of 'bool FilePathComparer.Equals(string x, string y)' doesn't match implicitly implemented member 'bool IEqualityComparer<string>.Equals(string? x, string? y)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'parameter' of 'bool CommandBase.CanExecute(object parameter)' doesn't match implicitly implemented member 'bool ICommand.CanExecute(object? parameter)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'parameter' of 'void CommandBase.Execute(object parameter)' doesn't match implicitly implemented member 'void ICommand.Execute(object? parameter)' (possibly because of nullability attributes).

Nullability of reference types in type of 'event EventHandler CommandBase.CanExecuteChanged' doesn't match implicitly implemented member 'event EventHandler? ICommand.CanExecuteChanged'.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.