Why can't [INotifyPropertyChanged] be used if something already implements the interface?

[nightowl286]

So the problem is that I can't use the attribute on a class that already implements the interface and I get the MVVMTK0001 error (among other ones if I try other workarounds) but is this check really necessary?

It prevents me from using my own interfaces (that then have a dependency on INotifyPropertyChanged) which makes it really annoying to use because then I have to structure my code in a specific way which obviously reduces the freedom of using the mvvm toolkit.

I can see why it might have been done so that there are no duplicate implementations of the interface, but surely just the regular C# errors would be enough for someone to realise that they have implemented it themselves as well.

[ToolmakerSteve]

FWIW: Its always good to show a code example that demonstrates the problem. This ensures everyone is discussing the same detail, and makes it easier to make suggestions.

[nightowl286]

As suggested, here is an example of the problem I was experiencing.

interface  ISomeInterface : INotifyPropertyChanged {
}

[INotifyPropertyChanged]
partial class SomeClass : ISomeInterface {
}

In this example, I get the MVVMTK0001 error (on the SomeClass class), which can be quite annoying when my interfaces specify that they need to implement INotifyPropertyChanged.

[smischke]

I support this feature request. If it's not possible in general, it would be helpful for me if Microsoft.Maui.Controls.BindableObject would be supported. I know, some hardcore MVVM fans may cry, but there's more than one way to get the job done.

Edit: Like https://github.com/canton7/PropertyChanged.SourceGenerator