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    <p>The way I do this is to have a central controller class that the ViewModels all know about, via an interface. I then set state into this before having the phone perform the navigation for me. Each ViewModel then interrogates this central class for the state it needs.</p> <p>There are a number of benefits to this for me:</p> <ul> <li>It allows me to have non-static ViewModels.</li> <li>I can use Ninject to inject the concrete implementation of the controller class and have it scoped as a singleton.</li> <li>Most importantly, when tombstoning, I only need to grab the current ViewModel and the controller class.</li> </ul> <p>I ran into a problem with messaging where my ViewModel was the registered listener, because I was View First and not ViewModel First, I was forced to use static ViewModel references. Otherwise the ViewModel wasn't created in time to receive the message.</p> <p>I use the controller class in conjunction with messages (it is basically the recipient of all messages around the UI) so in future if I refactor, I don't need to change much, just the recipients of the messages.</p> <p>Come to think of it, the controller class is also my navigation sink - as I have some custom navigation code that skips back paging on certain pages etc.</p> <p>Here's an example of my current set up:</p> <pre><code>public interface IController { Foo SelectedFoo { get; } } public class ViewModel { private IController _controller; public ViewModel(IController controller) { _controller = controller; } private void LoadData() { // Using selected foo, we load the bars. var bars = LoadBars(_controller.SelectedFoo); } } </code></pre>
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    1. POMVVM Light, Windows Phone, View & ViewModel navigation between pages
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    1. USAdam Houldsworth
    1. USAdam Houldsworth
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    1. COAlthough you are injecting the dependencies, your ViewModels should not be sourcing data from elsewhere as that breaks the separation and testability of the VMs. We generally have our controllers manage the VMs and stuff values into them rather than VMs drag in values from outside. The VMs should be as ignorant as possible. Just an opinion. Feel free to ignore :)
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      1. USGone Coding
    2. COIt is valid to have a ViewModel require something. I don't see a difference between having the ViewModel be given an interface to the source of information or the ViewModel relying on a message being received prior. As for testing, the interface can be mocked... so it is entirely testable.
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      1. USAdam Houldsworth
 

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