DelegateCommand. Something like "ObservesCollection"?

[jmo-gelsight]

I use DelegateCommand.ObservesProperty all the time. But I have a case where I wish there was something different. I'm wondering if there is but I just have missed it.

It happens when my view-models expose a command whose enabled status depends upon the content of an ObservableCollection also exposed by the same viewmodel. Some times these commands are only enabled when a certain number of items are in the collection. Others, only when a certain types of items are in it.

My typical workaround is to subscribe to INotifyCollectionChanged.CollectionChanged myself and manually update the command's status. Ideally, what I would like is for DelegateCommand to have a function called ObservesCollection() that would trigger a check whenever the collection in question sent out a CollectionChanged.

I was about to try to derive my own class from DelegateCommand to add this but am I missing some obvious way to do this?

[AmrAlSayed0]

Observing ObservesCollection.Count could work but I don't think they will work for replace operations.

[jmo-gelsight]

Can I use ObservesProperty on a property that belongs to another object? I was under the impression that I could only use ObservesProperty on my own properties, not on a property of a... property. I've always just written it as

ObservesProperty(() => SomePropertyOfMine)

Because frankly, Count might be enough if I could do something like this:

ObservesProperty(MyCollection => MyCollection.Count)

[AmrAlSayed0]

Yes, Prism supports responding to nested properties. In fact, it responds to all the properties in the property chain if each (or any) of these objects implement INPC interface.
.ObserveProperty(() => obj.Property1.Property2.Property3) would cause the .CanExecute to be revaluated on any change on any of the 3 properties.

[jmo-gelsight]

I have to admit, I feel awfully stupid for not realizing that I could do this. I never understood that ObservesProperty would actually be triggered for properties "that far down the chain". I will try this.

Still I might end up trying to implement my own ObservesCollection anyway, if only for sake of symmetry