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POFilling ObservableCollection through use of RX
 

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    <p>I was wondering if following scenario could be fixed by using RX?</p> <p>I have a REST service call that has an input parameter distance and loads data, this data is than inserted in the ObservableCollection of the ViewModel so that the View will show the data... Pseudo code like this:</p> <pre><code>public async Task&lt;int&gt; LoadData(int distance) { this.ListOnUI.Clear(); var dataList = await Task.Run(() =&gt; _dataService.GetListAsync(distance)); foreach(var dataItem in dataList) { this.ListOnUI.Add(dataItem); } return dataList.Count; } </code></pre> <p>Now this small code snippet is wrapped inside a method, that returns the count of the dataList. What I do with that count, check if the amount returned is at least 20, if not I recall the method with a larger distance.</p> <p>So what is wrong with this setup...</p> <ol> <li>Each time the method is called the UI list is cleared</li> <li>The user sometimes has to wait long until we reach 20 items</li> <li>While we haven't reached 20 items, the UI will act weird with the clearing of the list</li> </ol> <p>So my gut feeling is telling me this could be solved by using RX somehow, so that we 'chunk' load/add the UI list.</p> <p>But my knowledge of RX is not good enough to solve it... so any ideas?</p> <p>REMARK: When we call the LoadData service we are getting a JSON string that is then mapped to a collection of DataItems, so if we not clear the UI ObservableCollection and would just Add them with each itteration... we would get the same item multiple times in the list because it are newly constructed objects ( although with the same data ).</p>
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    1. COWhat specifically is the user experience you want? Are you looking to populate the list asap? So that if the first call returns say 10 items, and the second call returns 20 with some intersection, then you only modify the list (adding new items, and removing ones no longer present). Or something else? Why not return the List (`Task<IList<T>>` when it has 20 items and manage recall inside a loop in the Task, and populate UI with result?
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    2. COEach time there is data available I want to populate the UI, even if we not have retrieved 20 items yet... but recalling the LoadData call can take up time.
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    3. COOK. What is the signature of GetListAsync? Why it is wrapped in Task.Run if it is already async? Just to get off dispatcher?
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