Question

I am using a mvvm pattern for an application that sources its data from a sql ce database using the Entity Framework version 4. The WPF application only has one view (don’t need anymore as the app is not that big). I am displaying a collection of properties from the database in a listbox, by creating an observablecollection in my viewmodel and binding this. This works exactly as expected. The issue is that I now have another listbox (in the same view) that needs to be populated with Images for each property. To be clear, each property has a bunch of images, but each image is only assigned to one property.

What would be the best way to display the images, I thought maybe creating another observablecollection for the images, but I am not sure how I would then ensure that only images for the appropriate property are shown. Or should I simply bind the listbox to the Images property of each property (house)?

Cheers

    private void Load()
    {
        PropertyList = new ObservableCollection<Property>((from property in entities.Properties.Include("Images")
                                                          select property));
        propertyView = CollectionViewSource.GetDefaultView(PropertyList);
        if (propertyView != null)
            propertyView.CurrentChanged += new System.EventHandler(propertyView_CurrentChanged);           

        RaisePropertyChanged("CurrentContact");
        RaisePropertyChanged("SaleTitle");
        RaisePropertyChanged("Address");
        RaisePropertyChanged("AuctioneerName");
        RaisePropertyChanged("AgentName");
        RaisePropertyChanged("Price");
        RaisePropertyChanged("NextBid");
        RaisePropertyChanged("Status");
    } 

Answer 1

That sounds distinctly like a different responsibility (a master/details view). In the true spirit of MVVM I’d create a new View and a new ViewModel – perhaps:

PropertyImagesViewModel
    - public Property Property { get; set; }
    - public IList<Image> Images { get; set; }
    - public int SelectedIndex { get; set; }

PropertyImagesView

Don’t forgot to call RaisePropertyChanged() in each of the property setters

Also note that ObservableCollection does nothing if you aren’t manipulating the contents one-at-a-time. If all do you is update the entire collection all-at-once, then it gives you no tangible benefit.

Another thing – if you need to notify that all your properties changed:

RaisePropertyChanged(null);

will do the trick.