WPF list box bound to read only observable collection not updating.

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C#

WPF

ListBox

Hi guys,

I have a query and I'm sure I've had the issue before yet the results from googling are bringing up the same thing which I have already implemented (in a fashion).

I have a MVVM application and one of the V-VM's is to display some file listings.

The viewModel has a read only observable collection property which looks like this:

public ReadOnlyObservableCollection<TemplateFileViewModel> ListOfTemplates
{
     get
     {
         m_FileListing = new ObservableCollection<TemplateFileViewModel>();
         if (!String.IsNullOrWhiteSpace(TemplateDirectoryPath))
         {
              foreach (var s in Directory.GetFiles(TemplateDirectoryPath, "*.MyEXT", 
                          IncludeSubFolders ? SearchOption.AllDirectories : 
                          SearchOption.TopDirectoryOnly))
               {
                    m_FileListing.Add(new TemplateFileViewModel(s));
               }
         }

         return new ReadOnlyObservableCollection<TemplateFileViewModel>(m_FileListing);

    }
}

I also have a property "TemplateDirectoryPath" which looks like this:

public string TemplateDirectoryPath
{
     get { return m_TemplateDirectoryPath; }
     set
     {
         if (Equals(m_TemplateDirectoryPath, value) || !Directory.Exists(value)) return;
         m_TemplateDirectoryPath = value;
         OnPropertyChanged("TemplateDirectoryPath");
         OnPropertyChanged("ListOfTemplates");
     }
}

The idea is that when the TemplateDirectoryPath is updated it triggers a list box to refresh its contents, which is bound to the ListOfTemplates property on the view model.

No my understanding is that if I user the "OnPropertyChanged" event it should result in the view doing a data refresh.

My listbox is bound as follows:

<ListBox Grid.Column="0" ItemsSource="{Binding Path=ListOfTemplates, UpdateSourceTrigger=PropertyChanged}" ItemTemplate="{StaticResource TemplateFileDataTemplate}"/>

Why would this not be triggering an update on the screen? From what I can see it all appears correct, am I missing something really obvious?


Thanks