Infinite loop loading view when using View-First and View Context switching

Question

I have a curious scenario in an existing architecture that has been in development for a while now. The architecture uses View-First to support Caliburn Micro inside a custom MS Office app that uses WPF content in MS Office Task panes. Since there is no top-level Application object, I use a custom Bootstrapper and a set of surrogate top-level Content "hosts" inside each Task Pane. The View-First top-level hosts are each Conductors of a single item. Once the hosts are initialized when the application starts, I simply conduct single child into each one and from that point on utilize ViewModel-First approach to compose the content of each Task Pane.

I am now trying to introduce View Context switching to support alternate views, using the style of

<ContentControl cal:View.Context="{Binding TaskPaneState}" cal:View.Model="{Binding}" />

Where TaskPaneState is an observable property on my Viewmodels that can either resolve to "Maximized" or "Minimized".

I organized the view folders to support these contexts, so I have Minimized.xaml, Maximized.xaml, etc.

However, when testing this approach I am now getting an infinite loop when trying to resolve/load/bind:

2014-03-24 14:52:23.5904|INFO|Caliburn.Micro.Action|Setting DC of Corp.Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
2014-03-24 14:52:23.5904|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to Corp.Control.Design.Views.Book.BookDesignerView.
2014-03-24 14:52:23.6094|INFO|Caliburn.Micro.Action|Setting DC of Corp.Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
2014-03-24 14:52:23.6094|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to Corp.Control.Design.Views.Book.BookDesignerView.
2014-03-24 14:52:23.6314|INFO|Caliburn.Micro.Action|Setting DC of Corp.Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
2014-03-24 14:52:23.6314|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to Corp.Control.Design.Views.Book.BookDesignerView.
2014-03-24 14:52:23.6474|INFO|Caliburn.Micro.Action|Setting DC of Corp.Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
2014-03-24 14:52:23.6474|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to Corp.Control.Design.Views.Book.BookDesignerView.
2014-03-24 14:52:23.6664|INFO|Caliburn.Micro.Action|Setting DC of Corp.Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
2014-03-24 14:52:23.6664|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to Corp.Control.Design.Views.Book.BookDesignerView.
2014-03-24 14:52:23.6904|INFO|Caliburn.Micro.Action|Setting DC of Corp.Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
2014-03-24 14:52:23.6904|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to Corp.Control.Design.Views.Book.BookDesignerView.
2014-03-24 14:52:23.7104|INFO|Caliburn.Micro.Action|Setting DC of Corp.Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
2014-03-24 14:52:23.7104|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to Corp.Control.Design.Views.Book.BookDesignerView.
2014-03-24 14:52:23.7534|INFO|Caliburn.Micro.Action|Setting DC of Corp.Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
2014-03-24 14:52:23.7534|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to Corp.Control.Design.Views.Book.BookDesignerView.

I'm at a loss at to what might be causing this infinite looping.

EDIT:

So i've updated my solution to use the 2.0.x Beta version of Caliburn Micro, and I get better behavior, but still aberrant somewhat. The looping still occurs but not infinitely. I get about 250+ loops and then things settle down and the View loads. From what I can tell in the debugger, if I put a breakpoint on View.OnModelChanged and View.OnContextChanged, the debugger flips between these two breakpoints about 250+ times (seen in the log below). I've also tried using a TwoWay binding for View.Context but that seems to make no difference... Still scratching my head...

Here's latest log:

    2014-04-01 11:57:53.0681|INFO|Caliburn.Micro.Action|Setting DC of .Control.AddIn.Views.ObjectNavigationTaskPaneHostView to .Control.AddIn.ViewModels.ObjectNavigationTaskPaneHostViewModel.
    2014-04-01 11:57:53.0741|INFO|Caliburn.Micro.Action|Attaching message handler .Control.AddIn.ViewModels.ObjectNavigationTaskPaneHostViewModel to .Control.AddIn.Views.ObjectNavigationTaskPaneHostView.
    2014-04-01 11:57:53.0741|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|ObjectNavigationTaskPaneHostViewModel OnViewLoaded
    2014-04-01 11:57:53.0741|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|ObjectNavigationTaskPaneHostViewModel OnViewAttached
    2014-04-01 11:57:53.0741|INFO|Caliburn.Micro.ConventionManager|ViewModel bound on ActiveItem.
    2014-04-01 11:57:53.0741|INFO|Caliburn.Micro.Screen|Activating .Control.AddIn.ViewModels.ObjectNavigationTaskPaneHostViewModel.
    2014-04-01 11:57:53.0891|INFO|.Control.AddIn.Views.TaskPaneHostView|Entering : ActivateContent
    2014-04-01 11:57:53.0891|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|ObjectNavigationTaskPaneHostViewModel Queued content viewmodel ObjectNavigationViewModel
    2014-04-01 11:57:53.0891|INFO|.Control.AddIn.Views.TaskPaneHostView|Exiting: ActivateContent
    2014-04-01 11:57:53.1221|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|ObjectNavigationTaskPaneHostViewModel OnViewReady
    2014-04-01 11:57:53.1221|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|ActivateItem(ObjectNavigationViewModel '.Control.ViewModels.ObjectNavigation.ObjectNavigationViewModel')
    2014-04-01 11:57:53.1221|INFO|Caliburn.Micro.Screen|Activating ObjectNavigationViewModel '.Control.ViewModels.ObjectNavigation.ObjectNavigationViewModel'.
    2014-04-01 11:57:53.1591|INFO|Caliburn.Micro.Action|Setting DC of .Control.Views.ObjectNavigation.ObjectNavigationView to ObjectNavigationViewModel '.Control.ViewModels.ObjectNavigation.ObjectNavigationViewModel'.
    2014-04-01 11:57:53.1591|INFO|Caliburn.Micro.Action|Attaching message handler ObjectNavigationViewModel '.Control.ViewModels.ObjectNavigation.ObjectNavigationViewModel' to .Control.Views.ObjectNavigation.ObjectNavigationView.
    2014-04-01 11:57:53.1591|INFO|Caliburn.Micro.ConventionManager|ContentTemplate applied to Items.
    2014-04-01 11:57:53.1591|INFO|Caliburn.Micro.ConventionManager|SelectedItem binding applied to Items.
    2014-04-01 11:57:53.1811|INFO|Caliburn.Micro.Screen|Activating ObjectTypeNavigationViewModel 'Browse CONTROL classes by Type'.
    2014-04-01 11:57:53.3491|INFO|Caliburn.Micro.Action|Setting DC of .Control.Views.ObjectNavigation.ObjectTypeNavigationView to ObjectTypeNavigationViewModel 'Browse CONTROL classes by Type'.
    2014-04-01 11:57:53.3491|INFO|Caliburn.Micro.Action|Attaching message handler ObjectTypeNavigationViewModel 'Browse CONTROL classes by Type' to .Control.Views.ObjectNavigation.ObjectTypeNavigationView.
    2014-04-01 11:57:53.3661|INFO|Caliburn.Micro.Action|Attaching message handler ObjectNavigationViewModel '.Control.ViewModels.ObjectNavigation.ObjectNavigationViewModel' to .Control.Windows.Common.KCIContextMenu Items.Count:1.
    2014-04-01 11:58:05.0291|INFO|.Control.AddIn.Views.TaskPaneHostView|Entering : DeactivateContent
    2014-04-01 11:58:05.0291|INFO|.Control.AddIn.Views.TaskPaneHostView|Exiting: DeactivateContent
    2014-04-01 11:58:08.2491|INFO|Caliburn.Micro.Action|Setting DC of .Control.AddIn.Views.DesignerTaskPaneHostView: Active Designer to .Control.AddIn.ViewModels.DesignerTaskPaneHostViewModel.
    2014-04-01 11:58:08.2491|INFO|Caliburn.Micro.Action|Attaching message handler .Control.AddIn.ViewModels.DesignerTaskPaneHostViewModel to .Control.AddIn.Views.DesignerTaskPaneHostView: Active Designer.
    2014-04-01 11:58:08.2511|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|DesignerTaskPaneHostViewModel OnViewLoaded
    2014-04-01 11:58:08.2511|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|DesignerTaskPaneHostViewModel OnViewAttached
    2014-04-01 11:58:08.2511|INFO|Caliburn.Micro.ConventionManager|ViewModel bound on ActiveItem.
    2014-04-01 11:58:08.2511|INFO|Caliburn.Micro.Screen|Activating .Control.AddIn.ViewModels.DesignerTaskPaneHostViewModel.
    2014-04-01 11:58:08.2511|INFO|.Control.AddIn.Views.TaskPaneHostView|Entering : ActivateContent
    2014-04-01 11:58:08.2511|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|DesignerTaskPaneHostViewModel Queued content viewmodel BookDesignerViewModel
    2014-04-01 11:58:08.2511|INFO|.Control.AddIn.Views.TaskPaneHostView|Exiting: ActivateContent
    2014-04-01 11:58:08.2841|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|DesignerTaskPaneHostViewModel OnViewReady
    2014-04-01 11:58:08.2841|INFO|.Control.AddIn.ViewModels.TaskPaneHostViewModel|ActivateItem(BookDesignerViewModel(Basic Budget Example))
    2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Screen|Activating BookDesignerViewModel(Basic Budget Example).
    2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Action|Setting DC of .Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
    2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to .Control.Design.Views.Book.BookDesignerView. 

<snip around 500 lines> 

2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Action|Setting DC of .Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
    2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to .Control.Design.Views.Book.BookDesignerView.
2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Action|Setting DC of .Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
    2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to .Control.Design.Views.Book.BookDesignerView.
2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Action|Setting DC of .Control.Design.Views.Book.BookDesignerView to BookDesignerViewModel(Basic Budget Example).
    2014-04-01 11:58:08.2841|INFO|Caliburn.Micro.Action|Attaching message handler BookDesignerViewModel(Basic Budget Example) to .Control.Design.Views.Book.BookDesignerView.


<View finally loads >

Answer 1

I'm still testing, but I believe there were at least two problems that I have addressed.

First the ordering of the View's attached properties on the ContentControl seems to be important. This is the order I am using:

<ContentControl cal:View.Context="{Binding TaskPaneState}" cal:View.Model="{Binding}" />

I didn't need to use a TwoWay binding on the Context property.

Also, if for some reason the value of the Context property, as seen by the View.OnModelChanged doesn't resolve to a view that corresponds to a real view on your system, it is possible that the parent View is returned and causes recursion.

Currently I'm still testing but it looks stable for the time being.

Answer 2

So you have a viewmodel named BookDesignerViewModel and I assume you have BookDesignerView as your view. Then you have a folder called BookDesigner (purely for structure under the Views Folder) that has Max/Min .xaml (shortened) files contained in that BookDesigner folder?

Secondly have you tried settings the cal:View.Context="{Binding TaskPaneState, Mode=TwoWay}" ? I know in previous answers you asked why it was done considering the nature of notification to that Property in question, to be honest I hadn't put much thought into it because it was part of the examples that I had looked over while learning CM, it was example HelloScreens that shows view switching in full detail.