ViewModel property sort of fatal with VMDisconnectedException - visual-studio-2012

Question

EDIT 2: If you're looking for an answer to a similar problem, check Stuart's answer and my comments on it.
EDIT: I am actually getting a Mono.Debugger.Soft.VMDisconnectedException. I also recently installed Windows 8.1 and Resharper (though Resharper is suspended now).
When I access a very simple list property of my view model in my MVVMCross Xamarin iOS application, the program fails. It doesn't quit most of the time: it acts like it's running. The simulator has a black screen and there is no exception. If I breakpoint on if (messagesViewModel != null) source.ItemsSource = messagesViewModel.Messages; and then type messagesViewModel.Messages into the Immediate Window, everything stops, so I can tell it is failing at this line. If instead I "step over", it never moves to the next line.
I was having similar behavior when I was toggling this code in the MvxTableViewSource:
public override int RowsInSection(UITableView tableview, int section)
{
return 1;
}
My view model looks like this:
public class MessagesViewModel : MvxViewModel
{
private List<BaseMessage> _messages = null;
public List<BaseMessage> Messages
{
get
{
return _messages; //yes, I know I'm returning null
//I wasn't at first.
}
}
public MessagesViewModel()
{
}
}
This is my ViewDIdLoad on the MvxTableViewController:
public override void ViewDidLoad()
{
base.ViewDidLoad();
var source = new MessagesTableViewSource(TableView);
//was binding here, removed it for debug purposes
//failure on second line here
var messagesViewModel = ViewModel as MessagesViewModel;
if (messagesViewModel != null) source.ItemsSource = messagesViewModel.Messages;
TableView.Source = source;
TableView.ReloadData();
}
Some initialization code:
public class App : MvxApplication
{
public App()
{
var appStart = new MvxAppStart<MessagesViewModel>();
Mvx.RegisterSingleton<IMvxAppStart>(appStart);
}
}
public partial class AppDelegate : MvxApplicationDelegate
{
//empty functions removed.
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
Window = new UIWindow(UIScreen.MainScreen.Bounds);
var presenter = new MvxTouchViewPresenter(this, Window);
var setup = new Setup(this, presenter);
setup.Initialize();
var startup = Mvx.Resolve<IMvxAppStart>();
startup.Start();
Window.MakeKeyAndVisible();
return true;
}
}

Answer 1

I suspect whatever the error is, it isn't in any of the code you have posted.
I just created a simple ViewModel:
public class FirstViewModel
: MvxViewModel
{
private List<string> _items = new List<string>() { "One", "Two", "Three"};
public List<string> Items
{
get { return _items; }
set { _items = value; RaisePropertyChanged(() => Items); }
}
}
And a simple View:
[Register("FirstView")]
public class FirstView : MvxTableViewController
{
public override void ViewDidLoad()
{
base.ViewDidLoad();
// ios7 layout
if (RespondsToSelector(new Selector("edgesForExtendedLayout")))
EdgesForExtendedLayout = UIRectEdge.None;
var firstViewModel = ViewModel as FirstViewModel;
var source = new MessagesTableViewSource(TableView);
source.ItemsSource = firstViewModel.Items;
TableView.Source = source;
}
public class MessagesTableViewSource : MvxTableViewSource
{
public MessagesTableViewSource(UITableView tableView) : base(tableView)
{
tableView.RegisterClassForCellReuse(typeof(MessagesCell), new NSString("MessagesCell"));
}
protected override UITableViewCell GetOrCreateCellFor(UITableView tableView, NSIndexPath indexPath, object item)
{
return tableView.DequeueReusableCell("MessagesCell");
}
}
public class MessagesCell : MvxTableViewCell
{
public MessagesCell(IntPtr handle)
: base(handle)
{
var txt = new UILabel(new RectangleF(0, 0, 320, 44));
Add(txt);
this.DelayBind(() =>
{
this.CreateBinding(txt).Apply();
});
}
}
}
And this code runs fine...
I wouldn't completely trust the integration of Xamarin.iOS with the Immediate window - it is better now than it used to be, but I've seen several problems with it before.
Some things to possibly check:
does the above code work for you?
if it does, then what's in your BaseMessage and MessagesTableViewSource classes - perhaps they are causing the problem?
can you use Mvx.Trace("The list is {0}", messagesViewModel.Messages ?? "-null") to view the list? Can you use trace within the ViewModel property get - is it being called? Can you use trace within the ViewModel constructor?
are all your assemblies building against the same versions of things? Are all your assemblies definitely rebuilt? (Check "Build|Configuration Manager")- what version of Xamarin.iOS are you running in VS and in the Mac?