Cannot convert null literal to non-nullable reference type.

'MOriginator<int>' is obsolete: 'This class will be obsolete, use ICommand instead'

'MTextBoxEditor.PropertyChanged' hides inherited member 'ReactiveObject.PropertyChanged'. Use the new keyword if hiding was intended.

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

'ViewModelBase.PropertyChanged' hides inherited member 'ReactiveObject.PropertyChanged'. Use the new keyword if hiding was intended.

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

'MementoCommand<int>' is obsolete: 'This class will be obsolete, use ICommand with Memento instead'

'VoicerSelector.PropertyChanged' hides inherited member 'ReactiveObject.PropertyChanged'. Use the new keyword if hiding was intended.

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