Dispaly list of views that are deactivated

Topics: Prism v4 - Silverlight 4
Feb 9, 2012 at 12:27 PM

Hi

I'm using prism navigation in my silverlight app.  I've implemented the INavigationAware and IRegionMemberLifetime interfaces in my viewmodels.  When clicking a button I load a view into a region in my shell (contentcontrol) displaying data for a particular customer.

If i click the button again to load a view for a different customer into the region it replaces the view that I originally opened.  This view will only be deactivated because I have set KeepAlive to true in viewmodel.

I know I can pass data when I request a view and I can evaluate this in INavigationTarget and activate the view if it meets the criteria, but I would like to show a list of deactivated views where the user would click the item in the list and it would bring them back to that customer.  As only 1 view can be shown in a contentcontrol at a time(the way I want it) the user does not know how many or what views that are loaded but not activated.

These deactivated view must be held in some collection somewhere so is there a way to display these in a list and have it update when views are added or removed?

Thanks

Paul

Developer
Feb 9, 2012 at 5:55 PM


Hi Paul,

I believe a possible approach, could be to implement the IActiveware interface  in your views / viewmodels.

This interface contains an IsActive property that returns true when the implementer is active, and an IsActiveChanged event that is raised whenever the active state is changed. This updates will be caused by the RegionActiveAwareBehavior that will monitor the ActiveViews collection, and will update the IsActive property of the IActiveAware views/view models that enter or leave this collection.

Based on this, for example, you could create an extension method like in the following code snippet, that might help you retrieve the deactivated views collection from your region:

public static class RegionCustomExtensions
    {
        public static IEnumerable<object> GetInactiveViews(this IRegion region)
        {
            return region.Views.Where(view => !(view as IActiveAware).IsActive);
        }
    }

Also, for more information about implementing IActiveAware you could check the following resources:

I hope you find this helpful,

Agustin Adami
http://blogs.southworks.net/aadami


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public static class RegionCustomExtensions

    {

        public static IEnumerable<object> GetInactiveViews(this IRegion region)

        {

            return region.Views.Where(view => !(view as IActiveAware).IsActive);

        }

    }

Feb 9, 2012 at 9:53 PM

Hi Agustin

Thanks for the response and links they look promising.

The extention you posted returns IEnumerable<object>.  So if this is a list of views would I have access to the values of the public properties in the viewmodel attached to each view?  The reason I ask is that If I want to show a list of inactive views in a listbox I would be able to show CustomerID, Customer Name etc. so the user would know what record they are navigating to.

I could also subscribe to the IsActiveChanged event and when fired update the list of inactive views in the listbox.

Am I going in the right direction to acheive this funtionality?

Thanks

Paul

Developer
Feb 10, 2012 at 3:49 PM

Hi,

Based on my understanding, the returned views collections, isn't the most proper place to access the properties exposed in your view models, as these properties are intended to be consumed within your view.

In my opinion, as you mentioned subscribing to the IsActiveChanged event, to be notified when the IsActive state changes to update the list of inactive views in the ListBox, sounds like a good idea. For example every time this event is fired you could consume a shared service that contains the proper logic to keep your ListBox updated.

Regards,

Agustin Adami
http://blogs.southworks.net/aadami


Feb 10, 2012 at 4:06 PM

Thanks Agustin much appreciated

Paul