Question

So my app is basically a shell with a ContentControl that I populate with custom UserControl‘s depending on the user selection of a menu.

But now I’m having a weird behaviour.

I had attached the Content property of the ContentControl to a ViewModel property wich I instantiate on demand. That works great but I’m having two problems.

1. When I select one option of the menu it creates a new instance of the specified UserControl and set the Content property the shell. That works, cause I see the control and can interact with it, and when I select another option from the menu, it shows me the other UserControl, but, when I select again the previosly selected option it seems to be loading the same previously instantiated control (the right one but with the older input, and I’m doing a new XXXControl() before setting it as the Content property of the ContentControl.

2. I’m calling a ShowDialog() from inside the custom control via Commands (from the user control view model I call the view via MVVM Light messaging and then show the dialog), and that works. But when I try to close the dialog it show it again the same number of time I select different options from the menu.

For example, I start with A menu and show the dialog, then the close button works, then I goes to B menu and back to A, then the close button works at the second press (two ShowDialog() are being called) and so on…

I don’t know wich part of the code must I paste in order to give a little more of context to this post, but any input will be appreciated. I’m stuck with this (mine) bug.

Code

On the shell view:

<ContentControl Grid.Row="2" Content="{Binding CurrentView}" Margin="15,10"/>

On the shell ViewModel:

if (action == null || action == SEARCH_ACTION)
    {
        ActionsMenuSelected = SEARCH_ACTION;
        var view = new SearchDocumentView();
        CurrentView = view;
    }

On the inner view (SearchDocumentView):

public SearchDocumentView()
{
    InitializeComponent();
    Messenger.Default.Register<NotificationMessage<Entity>>(this, NotificationMessageReceived);
}


private void NotificationMessageReceived(NotificationMessage<Entity> msg)
{
    if (msg.Notification == "ViewResult")
    {
        var view = new DocumentViewer( ServiceLocator.Current.GetInstance<IDataService>(),msg.Content);
        view.ShowDialog();
    }
}

On the inner view (SearchDocumentView) xaml:

<ListBox x:Name="SearchResults"  ItemsSource="{Binding SearchResults}" SelectedItem="{Binding SelectedSearchResult}">
            <ListBox.InputBindings>
                <KeyBinding
                            Key="Enter"
                            Command="{Binding ViewResult}" />
                <KeyBinding
                            Key="Return"
                            Command="{Binding ViewResult}" />
            </ListBox.InputBindings>
            ...

On the inner view (SearchDocumentView) ViewModel:

private RelayCommand _viewResut;

        /// <summary>
        /// Gets the ViewResult.
        /// </summary>
        public RelayCommand ViewResult
        {
            get
            {
                return _viewResut
                    ?? (_viewResut = new RelayCommand(
                                          () =>
                                          {
                                              MessengerInstance.Send(new NotificationMessage<Entity>((Entity)SelectedSearchResult, "ViewResult"));
                                          },
                                          () => ((Entity)SelectedSearchResult!=null)?true:false ));
            }
        }

Answer 1

Why you see your old data I cannot see right now – but I guess you use the same (model)-data for the newly created view.

The second problem should be here:

public SearchDocumentView()
{
    InitializeComponent();
    Messenger.Default.Register<NotificationMessage<Entity>>(this, NotificationMessageReceived);
}

For each new view your register a Notification, that will show your message box but I don’t see if you unregister those and if you don’t the handler will hold the viewmodel in memory and will still show the messages boxes.

Even if I got it wrong (is this your “controls”-viewmodel?) it should be something very similar, but you can find this easily by setting a breakpoint to the .Show on your message and looking at the callstack while debugging.