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POCombining ObservableCollection<T> and List<T> in a MVC application
 

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    <p>I'm trying to display a list of alarms in a WPF ListVieuw. To accomplish this I databinded the Listbox to a property containing the list of alarms. Since I use the MVC programming paradigm the property is located in the controller, and the datacontext of the view is set to that controller.</p> <p>I noticed that when I added an alarm to the list, the view didn't display the new alarm. After some research I found I need to use the ObservableCollection class to do this correctly.</p> <p>However, displaying the list of alarms isn't the only thing that needs to be done with it, so I can't / don't want to change the variable type of the list to ObservableCollection.</p> <p>I now tried to make a property of the type ObservableCollection, but this doesn't work either. This is pretty normal, since I don't add the alarm to the property, I add it to the variable, which is still of the type List.</p> <p>Is there a way to tell the property when the List is updated, or an other/better way to display my alarms and keep them easy to use for other parts of the program?</p> <p>Edit:</p> <p>My workaround: I trigger the <code>PropertyChanged</code> event by clearing my property FutureEvents in the eventhandler of the <code>PropertyChanged</code> event from my alarms variable.</p> <p>My code: class cMain { private static volatile cMain instance; private static object syncRoot = new Object();</p> <pre><code> ObservableCollection&lt;Alarm&gt; alarms; #region properties /// &lt;summary&gt; /// Returns the list of alarms in the model. Can't be used to add alarms, use the AddAlarm method /// &lt;/summary&gt; public ObservableCollection&lt;Alarm&gt; Alarms { get { return alarms; } } /// &lt;summary&gt; /// Returns the ObservableCollection of future alarms in the model to be displayed by the vieuw. /// &lt;/summary&gt; public ObservableCollection&lt;Alarm&gt; FutureAlarms { get { //Only show alarms in the future and alarm that recure in the future var fAlarms = new ObservableCollection&lt;Alarm&gt;(alarms.Where(a =&gt; a.DateTime &gt; DateTime.Now || (a.EndRecurrency != null &amp;&amp; a.EndRecurrency &gt; DateTime.Now))); return fAlarms; } } /// &lt;summary&gt; /// Returns a desctription of the date and time of the next alarm /// &lt;/summary&gt; public String NextAlarmDescription { get { if (alarms != null) { return alarms.Last().DateTimeDescription; } else { return null; } } } #endregion //properties #region public /// &lt;summary&gt; /// Returns the instance of the singleton /// &lt;/summary&gt; public static cMain Instance { get { if (instance == null) //Check if an instance has been made before { lock (syncRoot) //Lock the ability to create instances, so this thread is the only thread that can excecute a constructor { if (instance == null) //Check if another thread initialized while we locked the object class instance = new cMain(); } } return instance; } } /// &lt;summary&gt; /// Shows a new intance of the new alarm window /// &lt;/summary&gt; public void NewAlarmWindow() { vNewAlarm newAlarm = new vNewAlarm(); newAlarm.Show(); } public void AddAlarm(Alarm alarm) { alarms.Add(alarm); } public void RemoveAlarm(Alarm alarm) { alarms.Remove(alarm); } public void StoreAlarms() { mXML.StoreAlarms(new List&lt;Alarm&gt;(alarms)); } #endregion //public #region private //Constructor is private because cMain is a singleton private cMain() { alarms = new ObservableCollection&lt;Alarm&gt;(mXML.GetAlarms()); alarms.CollectionChanged += new System.Collections.Specialized.NotifyCollectionChangedEventHandler(alarms_CollectionChanged); } private void alarms_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e) { FutureAlarms.Clear(); //Needed to trigger the CollectionChanged event of FutureAlarms StoreAlarms(); } #endregion //private } </code></pre>
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