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Editorial Team
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Asked: 2026-06-10T03:37:32+00:00

I’m creating a simple network application that communicates with one or more services, so

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I’m creating a simple network application that communicates with one or more services, so I planned to use some queues (for outgoing messages and incoming ones), a table, a list containing the status for each active connection, etc.: in other words, these are the data structures needed to ensure the functioning of the application itself.

This application must also be equipped with a graphical interface that shows part of the internal functioning of the application itself: for example, the filling status of queues, the status (detected speed, etc.) of the connections, etc.. According to the Model-View-ViewModel pattern, the model consists of the data to be displayed in the GUI: in this application, the aforementioned data structures represent the model. In other words, the Model implements the business logic of the application.

The ViewModel should implement INotifyPropertyChanged interface in order to notify the View that a change is occurred, but how does the Model to communicate with the ViewModel? After reading this article, I realize that the INotifyPropertyChanged interface is implemented by the model. This answer explains a little more, but it confuses me a bit:

INotifyPropertyChanged – Should go into ViewModel and Model (if needed)

Why, if needed?
When should I implement this interface?
When should I not implement it?

Moreover, the Dictionary does not implement the INotifyPropertyChanged interface: if I use it, should I wrap it with a class which implements this interface?

Finally, the model should be read-only, meaning that the user does not be able to change the contents of internal data structures using the GUI. How to accomplish this?

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1 Answer

  1. Editorial Team

    1. INotifyPropertyChanged is primarily implemented by the ViewModel classes. This is to facilitate the data-binding so that the UI controls in the view that are bound to the ViewModel property will be updated when the property is modified.
      In the MVVM design pattern, the relationships are very simple and in a single direction. The View knows it’s ViewModel and a ViewModel knows about the Model. If the Model is updated, the ViewModel needs to know somehow so that it can reflect the update and propogate it to the View. One way is to also have the Model implement INotifyPropertyChanged and have the ViewModel implement the corresponding event handler. If all the changes are driven from the UI and being pushed back to the Model, then this is probably not necessary.

    2. You can’t really bind to a Dictionary. Using an ObservableCollection would be ideal if that works in your case. Or, you can take a look at implementing an Observable Dictionary along the lines of this: http://drwpf.com/blog/2007/09/16/can-i-bind-my-itemscontrol-to-a-dictionary/

    3. MVVM has provided separation of the Model from the View, so there should be no direct relationship from the View to the Model. The implementation of the ViewModel controls what, if anything would ever get written back to your Model.

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