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copied!<p>To be straight to the point, creating new instance of the <code>ObservableCollection</code> every time your data changes then re-assigning it to the <code>ItemSource</code>, is not only disregarding core purpose of the <code>ObservableCollection</code>, it is also breaking/misusing the concept of <code>Data Binding</code>.</p> <pre><code>//this is the line I am talking about: var Items = new ObservableCollection<Item>(notUploadedItems); </code></pre> <p>Instead, create the <code>ObserbaleCollection</code> once -- make it a property:</p> <pre><code>private readonly ObservableCollection<Item> _items = new ObservableCollection<Item>(); public ObservableCollection<Item> Items {get {return _items;} </code></pre> <p>For the updates use collection's '.Add()' or 'Remove()' methods</p> <p>You're correct that you must be on the UI Main thread to do the updates:</p> <pre><code> DoItOnUIThread(() =>Items.Add(newItem)); //here's a sample of method that would take any action and execute it on UI thread.. private void DoItOnUIThread(Action action) { if (_dispatchService == null) _dispatchService = ServiceLocator.Current.GetInstance<IDispatchService>(); if (_dispatchService.CheckAccess()) action.Invoke (); else _dispatchService.Invoke(action); } </code></pre> <p>Let the observable collection do its job, which is automatically update the UI through Binding with new items and their property changes. If all that is hooked up/done properly your listbox shouldn't need to be updated in cs code at all.</p>

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