wpf - INotifyPropertyChanged vs. DependencyProperty in ViewModel

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Top 5 Answer for wpf - INotifyPropertyChanged vs. DependencyProperty in ViewModel

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93

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

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81

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

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

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78

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.

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67

From an expressiveness standpoint, I thoroughly enjoy using dependency properties and cringe at the thought of INotifyPropertyChanged. Apart from the string property names and possible memory leaks due to event subscription, INotifyPropertyChanged is a much more explicit mechanism.

Dependency properties imply "when this, do that" using easily-understood static metadata. It is a declarative approach that gets my vote for elegance.

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56

Dependency properties are intended to supports binding (as a target) on UI elements not as a source to data binding, this is where INotifyProperty comes in. From a pure point of view you shouldn't use DP on a ViewModels.

"In order to be the source of a binding, a property does not need to be a dependency property; you can use any CLR property as a binding source. However, in order to be the target of a binding, the property must be a dependency property. For a one-way or two-way binding to be effective, the source property must support change notifications that propagate to the binding system and thus the target. For custom CLR binding sources, this means that the property must support INotifyPropertyChanged. Collections should support INotifyCollectionChanged."

All dependency objects cannot be serialised (This could hamper the use of ViewModels and DTO (POCO)'s.

There are differences between DP within Silverlight compared to WPF.

http://msdn.microsoft.com/en-us/library/cc221408(v=VS.95).aspx

http://msdn.microsoft.com/en-us/library/cc903933(VS.95).aspx

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