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  1. PO
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    <p>The problem is in your <code>this.Combinations.Clear();</code><br> When you do it, it sets <code>SelectedItem = null</code> and <code>SelectedIndex = -1</code> </p> <p>So you should set selection again. If you have an access to your ComboBox then just write this <code>cbCombination.SelectedIndex = 0;</code> after filling Combinations list.<br> Of course you can bind SelectedItem/SelectedIndex to some property in code behind too.</p> <p>BTW<br> Also it is not required to call <code>NotifyPropertyChanged(@"Combinations");</code> after filling the collection because <code>Combinations</code> already implements <code>INotifyPropertyChanged</code>.</p> <p><strong>Update</strong></p> <p>To detect that your <em>ObservableCollection</em> was changed, subscribe to <em>CollectionChanged</em> event in your <em>UserControl</em> code behind. Make sure that you subscribed <strong>before</strong> collection changed!</p> <pre><code>Combinations.CollectionChanged += (s, e) =&gt; { if (cbCombination.Items.Count &gt; 0) cbCombination.SelectedIndex = 0; }; </code></pre> <p><strong>Another suggestion</strong></p> <p>Approach above is works when you do not need a smarter logic than just select zero index in combobox. But often you will need a more complex logic to select some item. In this case you may add new property to your model: </p> <pre><code>public Combination SelectedCombination { get{ return _selectedCombination; } set { _selectedCombination = value; NotifyPropertyChanged("SelectedCombination"); } } </code></pre> <p>and bind this property to your combobox:</p> <pre><code>&lt;ComboBox Name="cbCombination" ItemsSource="{Binding Combinations}" SelectedIndex="0" SelectedItem={Bindings SelectedCombination} /&gt; </code></pre> <p>In this case you can select any item when filling the Combinations collection and it will be automatically selected in combobox:</p> <pre><code>var combinationsList = CombinationsManager.CombinationsFor(someParam); this.Combinations.Clear(); foreach (var combination in combinationsList) this.Combinations.Add(combination); if (Combinations.Count &gt; 0) SelectedCombination = Combinations[0]; </code></pre>
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    1. POCombo-box loses selection after collection changes
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    1. USasktomsk
    1. USasktomsk
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      1. VTUpMod
    1. COThanks, but: I AM trying to set the selection again, but how? What should wakes up my code that will modify SelectedItem and / or SelectedIndex? My whole issue is that the combo box's SourceUpdated event doesn't fire!
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    2. COIt probably fires but your putting a breakpoint in the setter of Combinations and that won't fire if the collection changes, only if you assign it another collection. Use selectedindex, selectedvalue or selecteditem in code.
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      1. USSilvermind
    3. COI've updated the answer. If it still not enough to solve the issue let me know.
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      1. USasktomsk
 

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