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I'm going to start to develop a WPF real time C# application for trading in stock exchange. I'm going to develop this application according to MVVM pattern. So in Model part of the MVVM application I should create data structures that View Model part should process, fill with data and so on.

One of the main parts of the stock exchange trading application is receiving of trading data from the stock exchange via special gate software library.

So I'd like to know where I should allocate this trading data receiving in my application: in the Model part where the receiving operation will fill the Model data structures and the View Model will take these filled data structures to process them? Or I should allocate this trading data receiving in the View Model part of the application where the View Model itself will fill processed data structures initially gotten empty from model?

Which way is more canonical from the viewpoint of the MVVM pattern?

Robert Harvey
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user1688773
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  • If you have Visual Studio 2010, I would highly recommend [MVVM in the box](http://karlshifflett.wordpress.com/2010/11/07/in-the-box-ndash-mvvm-training/), it's just awesome! – JMK May 13 '13 at 14:41
  • I suppose to use Visual Studio 2012 due to nice MVVM Toolkit Light for this version of Visual Studio. – user1688773 May 15 '13 at 12:50

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IMO This would be the responsibility of the Model. The VM is a bridge between Model and View and it's mainly responsible for handling logic for the View(User invoked stuff).

Business logic(not invoked by the user) should reside in the Model.

In your case when you say have web services for getting data these should interface with the Model and should be Services pretty much that the Model should be accessing for updated data.

Viv
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  • I would disagree with adding the web services to the actual Model; let the VM perform the work and update the Model values as needed. This will help decouple the Model from any type of data logic and allow the Model to be re-used without having to incorporate the embedded web services. – Metro Smurf May 13 '13 at 15:36
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    well your not "adding" the service to the Model. All your doing is wrapping the actions of "receiving updated stock data" into a service which the Model "uses" not "has within". Also with having this logic in the VM(Which isn't a user invoked action), what comes in the future if the OP adds a new VM for a different layout View? We'd need to duplicate code in this VM to the new VM or abstract functionality out then. If the code is in the Model then the VM just gets "plugged into" the current application than involve more refactoring. It boils down to personal preference I'd guess – Viv May 13 '13 at 15:49
  • Thanks. I'll study the application structure more intently. In case of web or Windows service - how the service will able to interact with Model part of application? Unfortunately I havn't had deal with web or Windows services programming before. – user1688773 May 15 '13 at 12:26
  • Can the Model part of MVVM application interact with web or Windows service wthout slowdown working of the service? Let the receiving of trading data via special gate library is implemented on Windows service. Because trading data is coming from stock exchange with high frequency, the Model is refering to service for the data very often. So it can significantly decelerate the working of service. Am I right? – user1688773 May 15 '13 at 12:46
  • @user1688773 well that just depends on how your code is. If your threading efficiently and not doing intensive stuff on the UI thread too often and delegating when appropriate to workers then things should be smooth. It's just too broad of a question to say yeh do X and Y to get to your solution. As for the interactions you can have your service implement an Interface that the Model / VM according to your preference holds and works with thereby not having a direct dependency to a fixed type. – Viv May 15 '13 at 13:10
  • I don't know that web or Windows service meets my requirements because in some event hamdlers of gate library some values are computed often and these values must map in to View part of application. – user1688773 May 15 '13 at 16:14
  • For multithreaded processing in my application I'm going to use TPL. – user1688773 May 15 '13 at 16:18
  • I think your misunderstanding the "service" meaning in this context. Have a look at http://stackoverflow.com/questions/925017/what-exactly-are-wpf-services "A service is just something that implements an interface that you can thus use to action requests with - not a typical windows service you find in your task manager" – Viv May 15 '13 at 23:07