How to get rid of INotifyPropertyChanging?

[mikeKuester]

Hi,
I'm just starting with the MVVM Community Toolkit and looking for a way to get rid of the INotifyPropertyChanging implementation.

Lets say I have a large number of instances of a view models and want to force the source generator, just to implement the code for INotifyPropertyChanged, but not for INotifyPropertyChanging. I know, that the "changing" events will never be used and in order to improve the performance, I don't want all these OnPropertyChanging calls.

Instead of inheriting from ObservableObject, I tried to use the INotifyPropertyChangedAttribute for the class and the generated code looks as expected - but then I got this MVVMTK0032 MVVM Toolkit warning: you don't implement a base type, so you should inherit from ObservableObject

The resulting code is not the same: using the INotifyPropertyChanged attribute or inheriting from ObservableObject. Therefore I think the warning from the MVVMTK0032 analyzer is not valid.

The warning is ok if I use the ObservableObject attribute for a class without a base type, but not for the INotifyPropertyChanged attribute.

Is there anything what I'm missing here?

Thank for your work for the toolkit and
best regards,
Mike

[Sergio0694]

"I know, that the "changing" events will never be used and in order to improve the performance, I don't want all these OnPropertyChanging calls."

That is unlikely to make any observable difference, especially if you're using the source generator for your observable property. That's because the generator will also generate and cache all the PropertyChangingEventArgs for each property, so the OnPropertyChanging call will simply do nothing. As in, it will see the event is null, and just not even raise it at all.

On the other hand, using ObservableObject is recommended because it allows you to reuse the same base code across all your viewmodels, whereas if you used [INotifyPropertyChanged] in each of them, you'd end up duplicating a lot of code and increasing your binary size unnecessarily.

I would recommend just inheriting from ObservableObject and using [ObservableProperty].

If you really want to, you can also set "MVVMTOOLKIT_DISABLE_INOTIFYPROPERTYCHANGING" in your app context switches. This will make the whole feature be completely disabled, so that even direct calls from other places will just not do anything 🙂

[mikeKuester]

Thanks for your fast answer!

Ok, if its not making an observable difference, that sounds good. And you're right - the caching of the PropertyChangingEventArgs is the main key here.