c# mvvm how to pass model to viewmodel

Question

I have read a lot about MVVM in the past, but I am not completely getting there. I looked at MVVM Light framework and understood the pattern of the ServiceLocater to bind View and Viewmodel. But I didnt find anything helpful about the connection between the model and the viewmodel.

So far I know that the Viewmodel should have a private "Model" instance and some public properties to be read by the View. The Model should implement the INotifyPropertyChanged event to notify the Viewmodel, which can do something with the data and/or change its public properties and notify the view.

I hope I got it right so far. But: Where is the Model created? and how does the Viewmodel gets the Model? Does the Viewmodel creates it? My Application gets data via bluetooth continously and process them in the background. At different process-stages it changes different Models. My first approach was a Singleton which holds all Models. The Viewmodel gets the Model from the Singleton and the Background-process can access the Model too. But I think that "pattern" is really bad.., but i cannot find any solution to do this "nice". I dont know how to share the model between the viewmodel and the background-process (businessLogic) properly.

I am glad about any help :)

Answer 1

As far as I know and use to do in our WPF projects - classical MVVM delegates Model creation on ViewModel. ViewModel should be Model-aware. Sometimes ViewModel could rely on ServiceLocator or DependencyInjection patterns to find out and create Model class (ie by interface).