Semantic Zoom Catastrophic failure on empty group - windows-8

Question

I am using the SemanticZoom control with a grid view and collection view source. All is working fine until I attempt to select ('jump to') an empty group - this causes an unhandled Catastrophic failure.
http://social.msdn.microsoft.com/Forums/nb-NO/winappswithcsharp/thread/6535656e-3293-4e0d-93b5-453864b95601
Does anybody know if there is a way to fix this - I want to 'allow' an empty group if I can.
Thanks

Answer 1

Okay, so I ran into this issue and fixed it. I know this is quite an old thread, but I'll answer it in case someone else runs into this. Here's how I did it.
The issue seems to be that the group set as the DestinationItem needs to have items in it. In the case that this group is empty, this poses a problem. The problem does not occur when the group is in between other filled groups, because it has a length of 0 and therefore is untargetable. When it is at the end (or possibly the beginning, haven't tried that), this poses an issue because the GridView/ListView targets the last one in the list when the mouse is past the end of the view.
So, how to solve it:
You need to add an event handler for OnViewChangeStarted. In this handler, you will have access to the SemanticZoomViewChangedEventArgs.
The first thing you need to do is find out if the Group being targetted is empty. I am using a custom Group class here, but have cast it to IEnumerable, just because I only need to know how many items are in it. Linq allows me to find the count of the IEnumerable.
using System.Linq;
private void Zoom_OnViewChangeStarted(object sender, SemanticZoomViewChangedEventArgs e)
{
var group = e.DestinationItem.Item as IEnumerable;
if (group != null && group.Count() == 0)
{
e.DestinationItem.Item = MyViewModel.Groups.Last(itemGroup => itemGroup.Count() > 0);
}
}
As you'll note, the next step is to set the DestinationItem.Item to the Last group that has items in it. You may also want to handle the First group that has items in it, but that's quite easy to do as well. In place of MyViewModel, insert your ViewModel. In place of Groups, insert your collection property.
I hope this helps and happy coding!