C# 4.0 .net 4 and WPF UI update

Question

Hello ,

I'm trying to build an app to work with twitter like site , and the problem I'm trying to solve is - How am i going to update the UI with a background worker and only add show the latest posts(tweets if you will ) on top of the wrap panel without removing the ones that already exist?

in my previous attempt i have done this by storing the tweets/posts in a local SQlite database and then retrieving the last 10 posts which causes the UI to freeze for a bit and reload all the posts.

Any ideas ?

Answer 1

Since you're using WPF, this is fairly easy.

Just store your "posts" in an ObservableCollection<T>. You can then just Insert the new item at the front of the list. If you've bound this to an ItemsCollection control, WPF will handle redrawing everything correctly for you.

Unless you have a LOT of elements, this will work quite well, and be fairly fast. I'd try it first (since it's really easy to implement), and only try to get more "clever" if you find that it has performance problems. I doubt you'll have issues, though, provided you use the proper collections, since WPF's data binding to ObservableCollection is quite fast.

Answer 2

Use databinding. The UI elements are databound to fields of a record in a collection. The panel of multiple rows should be an ItemCollection of some sort - Listbox, most likely - so that it will replicate the item data template for each row in the underlying data collection.

After that, the UI will track with any changes made to the underlying collection, if the collection implements INotifyCollectionChanged. If you use an in-memory collection, you can just add new data to the top of the collection (Insert at index 0) and that will push all the old items down in the UI display. If you use a file or server based data source, you can fetch the data in a background thread and post updates to the in-memory collection on the foreground thread. Just don't update the databound collection from the background thread.