INotifyPropertyChanged vs. DependencyProperty in ViewModel

When implementing the ViewModel in a Model-View-ViewModel architecture WPF application there seem to be two major choices how to make it databindable. I have seen implementations that use DependencyProperty for properties the View is going to bind against and I have seen the ViewModel implementing INotifyPropertyChanged instead.

My question is when should I prefer one over the other? Are there any performance differences? Is it really a good idea to give the ViewModel dependencies to WPF? What else do I need to consider when make the design decision?

Solution 1:

Kent wrote an interesting blog about this topic: View Models: POCOs versus DependencyObjects.

Short summary:

1. DependencyObjects are not marked as serializable
2. The DependencyObject class overrides and seals the Equals() and GetHashCode() methods
3. A DependencyObject has thread affinity – it can only be accessed on the thread on which it was created

I prefer the POCO approach. A base class for PresentationModel (aka ViewModel) which implements INotifyPropertyChanged interface can be found here: http://compositeextensions.codeplex.com

Solution 2:

According to the WPF performance guide, DependencyObjects definitely perform better than POCOs that implement INotifyPropertyChanged:

http://msdn.microsoft.com/en-us/library/bb613546.aspx

Solution 3:

The choice is totally based on your business logic and UI abstraction level. If you dont want a good separation then DP will work for you.

DependencyProperties will be applicable mainly at the VisualElements level so it won't be good idea if we create lot of DPs for each of our business requirements. Also there is a greater cost for DP than a INotifyPropertyChanged. When you design a WPF/Silverlight try to design UI and ViewModel totally separate so that at any point of time we can change the Layout and UI controls (Based on theme and Styles)

Refer this post also - https://stackoverflow.com/questions/275098/what-applications-could-i-study-to-understand-datamodel-view-viewmodel . The link has a lot of reference to Model-View-ViewModel pattern, which is very relevant to this discussion.