How to handle bindable application wide variables in a WPF MVVM application?_问答_开发者

I am writing a fairly large scale WPF desktop application using the MVVM pattern. I have been stuck for a while on getting my common properties to update in a View other than the one that updated it.

I have a RibbonWindow MainView that contains a ContentControl that displays the remaining Views one at a time dependant on the user's selection. I have a BaseViewModel class that all the ViewModels extend. Among other things, this class exposes the INotifyPropertyChanged interface and contains a static property of type CommonDataStore. This class also implements the INotifyPropertyChanged interface and contains the properties that are to be available to every ViewModel.

Now, although I can access and successfully update the CommonDataStore properties from any ViewModel, the problem is that the WPF Framework will only notify properties that have changed in the current View. Therefore, although the common values have been updated in other ViewModels, their associated Views do not get updated.

One example from my application is the login screen: As the user logs in, my LogInView updates with the new information (ie. full name) from the database, but the user details in the MainView do not.

After reading a few other posts, I also tried implementing the CommonDataStore class as a Singleton, but that didn't help. I could also just pass a reference to this common data object to the constructor of each ViewModel from the MainViewModel, but I'm not sure if this is the right way to go.

I have also discovered that in WPF, static properties are treated a bit like constant values. It seems that they just read the value once.

So anyway it's clear, my attempts have all failed. I was wondering what the standard way of d开发者_如何学Coing this was? In particular, I need to be able to bind to the common properties and have all of my ViewModels and Views update when any common value is changed. Any help would be greatly appreciated. Many thanks in advance.

Edit >> Really? No one uses application wide variables in an MVVM WPF application?

I have now removed the static part of the Common property declaration and am simply passing a copy into each ViewModel individually. This seems to work, but I'd really like to know how others approach this situation. Please answer by simply letting me know how you organise this application wide data.

I have done something similar to what you describe last. I have class called SecurityContext that holds some of the application-wide data. One instance is created when the application starts up and then that instance is passed into the constructors of all the ViewModels through dependency-injection. I have a base class for ViewModels which exposes that object through a regular instance property (implementing INotifyPropertyChanged).

Have you looked into implementing the Observer Pattern? We have done so with IObservable and IObserver. This describes the "IObservable/IObserver Development Model" as follows:

The IObservable/IObserver development model provides an alternative to using input and output adapters as the producer and consumer of event sources and sinks. This model is based on the IObservable/IObserver design pattern in which an observer is any object that wishes to be notified when the state of another object changes, and an observable is any object whose state may be of interest, and in whom another object may register an interest. For example, in a publication-subscription application, the observable is the publisher, and the observer is the subscriber object. For more information, see Exploring the Observer Design Pattern on MSDN.