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POLINQ filtering in IEnumerable property breaks binding
 

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  1. POLINQ filtering in IEnumerable property breaks binding
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    <p>I have a <code>TextBlock</code> in my UI bound to the <code>.Count()</code> extension of a property. I would like to add LINQ filtering to the property, but when I do it breaks the binding.</p> <p>This works and updates the UI without any problems:</p> <pre><code>public IEnumerable&lt;Worker&gt; WorkersTest { get { return DataManager.Data.Workers; } } </code></pre> <p>After adding LINQ filtering, <code>WorkersTest</code> does not update the <code>TextBlock</code>, though a MessageBox confirms that the property is being modified. Upon initialization of the data, however, the value displays correctly:</p> <pre><code>public IEnumerable&lt;Worker&gt; WorkersTest { get { return DataManager.Data.Workers.Where(w =&gt; w.Gender == Gender.Male); } } </code></pre> <p>Is there any way to keep the LINQ filtering without breaking the binding?</p> <p><strong>Update:</strong> One thing that I need to clarify is that <code>DataManager.Data.Workers</code> is an <code>ObservableCollection</code>.</p> <p>From what I can tell, any LINQ operation breaks the binding with the exception of <code>AsEnumerable()</code>, which doesn't have any effect.</p> <p>Also, in response to Andres' answer, <code>Count()</code> isn't the problem. If I bind this property to a <code>DataGrid</code>, I get the same results. With LINQ, it doesn't update. Without LINQ, it does. Is there any sort of workaround for this, preferably one that doesn't involve <code>ICollectionView</code> or anything of that nature?</p> <p><strong>Update:</strong> Does anybody know if LINQ extensions such as <code>Where</code> return new objects when used? I haven't been able to find any documentation of this online. If this is the case, however, that may be the problem.</p> <p><strong>Update:</strong> I inserted a breakpoint and found some interesting information that may be useful:</p> <p>Without LINQ:</p> <p><img src="https://i.stack.imgur.com/IMsEb.png" alt="enter image description here"></p> <p>With LINQ:</p> <p><img src="https://i.stack.imgur.com/nN29H.png" alt="enter image description here"></p> <p><img src="https://i.stack.imgur.com/JkARU.png" alt="enter image description here"></p> <p>Perhaps this can shed some light on what's really going on and hopefully get me closer to the solution.</p> <p>Would I be correct in assuming that <code>CollectionChanged</code> and <code>PropertyChanged</code> being null is the source of the problem? If so, what can I do to fix that?</p>
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    1. USJason D
    1. USJason D
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    1. COIs your binding mode set? Mode=TwoWay.
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      1. USGuilherme H. J.
    2. COThat throws an InvalidOperationException. The Count property is read-only.
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      1. USJason D
    3. COLinq query will be lazy, it does nothing until it is evaluated i.e you call ToList(). Also Binding to a query like that is not very good. Bind to a property that raises PropertyChanged event in INotifyPropertyChanged: http://msdn.microsoft.com/en-us/library/system.componentmodel.inotifypropertychanged.aspx this will tell the UI it needs to update.
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      1. POLINQ filtering in IEnumerable property breaks binding
      1. USMark Homer
 

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