How to detect if an item in my ObservableCollection has changed

• Implement INotifyPropertyChanged in your Product class with notification for every property.
• Implement INotifyPropertyChanged in your viewmodel.
• Add property IsDirty to your ViewModel (with notification through INotifyPropertyChanged.

• In your viewmodel, subscribe to CollectionChanged

  public YourViewModel(){    ...    YourCollection.CollectionChanged += YourCollection_CollectionChanged;     ...}private void YourCollection_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs args){    if (args.OldItems != null)        foreach(var oldItem in args.OldItems)            oldItem.PropertyChanged -= YourItem_PropertyChanged;    if (args.NewItems != null)        foreach(var newItem in args.NewItems)            newItem.PropertyChanged += YourItem_PropertyChanged;}private void Youritem_PropertyChanged(object sender, System.ComponentModel.PropertyChangedEventArgs args){    IsDirty = true;}

• Now you can bind to IsDirty property of your viewmodel, for example, you can bind Button.IsEnabled property directly to it.

Just use the ObservableCollection.It has an event called CollectionChanged. If you register it, you can do what you want. Example:

ObservableCollection<string> strings = new ObservableCollection<string>();strings.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(changed);strings.Add("Hello");strings[0] = "HelloHello";

And:

private void changed(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs args){    //You get notified here two times.}

The logic needs to go in your Model (Product class).A clean approach would be to expose IsDirty property (backed by field) in your model.

And your ViewModel would have a Command binding with CanSave checking the internal collection, and return true if Any of the item in collection IsDirty=true.