Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

David Anson — Mon, 24 Dec 2012 05:20:09 GMT

Kishore Joshi,

You *might* be able to use the Silverlight Toolkit's Expander control for this, but I kind of doubt it because that would break the ListBox metaphor. The technique I show here is more of a hack than anything else and trying to go further with it could be more trouble than it's worth... :) Maybe consider using a TreeView instead as that supports expand/collapse natively..

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

Kishore Joshi — Fri, 21 Dec 2012 17:43:27 GMT

Thanks for the suggestion. there was a custom class in middle I changed it and not its working good.

David,

Can you suggest how can I implement a expand collapse feature on the group headers.

Thanks.

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

David Anson — Fri, 21 Dec 2012 05:53:15 GMT

Kishore Joshi,

Set a breakpoint on the first line of GroupingItemsControlConverter.Convert. If the value parameter has the data you expect, then the problem could be in GroupingItemsControlConverter and you can step through the code there. If it's not called or the value parameter is null (which is what I'm guessing will happen), then the issue is probably that the data change isn't propagating through the Binding to get into the converter in the first place. The most common reason for this is changing a property on a model object and not firing the PropertyChanged event for it. If you're setting DataContext directly, the change should flow through automatically, but if you have a custom class in the middle, I'd look there for a problem like this.

Good luck!

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

Kishore Joshi — Thu, 20 Dec 2012 22:26:14 GMT

Great post. thanks for source code and explanation.

David, I implemented the GroupConverter and have one issue.

The point were you set the data context, your ex it was a static array. In my case a async job returns an object and I parse throw to make an array of similar structure. But the groupconverter do not wait for the object and fails to show anything. Can you suggest something in this case.

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

David Anson — Fri, 24 Jun 2011 04:11:00 GMT

Brandon,

No worries - glad you've got it working! :)

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

Brandon — Fri, 24 Jun 2011 01:20:37 GMT

Wow, seriously, I completely left out the field I'm grouping on from my test data, sorry for wasting your time! Thank you very much for your help though!

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

Brandon — Fri, 24 Jun 2011 00:34:11 GMT

Thanks David, I'll give it a shot, it works beautifully runtime, but I'd just like to get Blend to show it to tweak my interface. I'll try out your suggestions right now.

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

David Anson — Thu, 23 Jun 2011 16:43:42 GMT

Brandon,

I *think* Blend runs IValueConverters on the design surface, so I'd expect this to work. What I'd recommend is removing the GroupingItemsControlConverter to be sure everything else is hooked up right in order to show the test data at design-time; sometimes that can be a little tricky to get right. Once that's working, drop in the GroupingItemsControlConverter and things should work. If not, then try running the app to verify that the run-time behavior is correct - if that doesn't work, then something's not hooked up right which is probably why it's not working.

Hope this helps!

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

Brandon — Thu, 23 Jun 2011 12:07:01 GMT

Will generating the listbox in this way allow for Blendability? I can't seem to get my test data to show up in my grid and I'm wondering if Blend just can't put the logic together for this one, or if I've missed something else I'd need to statically define.

Thanks.

re: Confessions of a ListBox groupie [Using IValueConverter to create a grouped list of items simply and flexibly]

David Anson — Mon, 23 May 2011 16:48:18 GMT

Veri,

Yes, you can use this idea/code on Windows Phone - and I know of others who have done so. :) The sample is a Silverlight 4 project, but the file you really want to reuse is GroupingItemsControlConverter.cs and it doesn't contain any references to AssemblyPart. It sounds like maybe you tried to reuse a part of the sample that was specific to desktop Silverlight - if you add only GroupingItemsControlConverter.cs to your Windows Phone project, you should be fine.

Good luck!