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POHow to bind to a collection without using an index of the collection?
 

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  1. POHow to bind to a collection without using an index of the collection?
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    <p>I am trying to learn the MVVM pattern in WPF and I am running into some issues with bindings and collections. I don't like binding to the index of the collection because the collection changes.</p> <p>I have <code>MyModelClass : ObservableCollection&lt;MyData&gt;</code></p> <p>The <code>MyData</code> class has a property called <code>DataValue</code> in it to hold my custom information. I fill the <code>MyModelClass</code> with <code>MyData</code> objects. In the view model class (<code>MyViewModel</code>) I have a property <code>CurrentData</code> of type <code>MyModelClass</code>. </p> <p>Now in this case, my binding is to a combo box. Here is what the binding looks like:</p> <pre><code>&lt;ComboBox Name="cmbxData" ItemsSource="{Binding Path=CurrentData}" DisplayMemberPath="DataValue" SelectedValuePath="DataValue" SelectedValue="{Binding Path=CurrentData[0].DataValue}"/&gt; </code></pre> <p>This all works fine and the <code>MyViewModel</code> class has the interface setup for PropertyChanged notifications. I need to refresh the information this holds every few seconds. </p> <p>I am refreshing the collection by doing something like this inside the <code>MyModelClass</code>:</p> <pre><code>public Class MyModelClass : ObservableCollection&lt;MyData&gt; { private static MyModelClass current = null; public static MyModelClass Current { get { if(current == null) current = new MyModelClass(); return current; } } private void UpdateModel(MyData newData) { MyModelClass newModel = new MyModelClass(); newModel.Add(newData); current = newModel; } } </code></pre> <p>Inside <code>MyViewModel</code> there is this:</p> <pre><code>MyModelClass CurrentData = MyModelClass.Current; </code></pre> <p>I tried my best to give as much code as I could and keep it simple. Please let me know if there is more needed to clarify. Thank you for any suggestions on how to fix my issue. </p> <p>In case you missed it: Problem: How can I bind to the collection, or the value I want to display in the collection, without using the index like I have shown above (<code>SelectedValue="{Binding Path=CurrentData[0].DataValue}"</code>)? How can I fix this or change my implementation to be correct?</p> <p>Thanks,</p>
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    1. UStherealjohn
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    1. COWhy are you implementing a collection type when you only want one item in the collection? If you want the current item you need another property which points to the current item
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      1. POHow to bind to a collection without using an index of the collection?
      1. USCharleh
    2. COI agree this is confusing to me also, but that is another problem I had where I was unable to get the binding to update when the properties changed unless it was in a collection. However, that is a separate problem from this question.
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      1. UStherealjohn
 

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