title: How to use CompositeCollection in WPF and MVVM
body: <p>I have a WPF app using MVVM. I have a DataGrid on the form and the DataGrid has a column with a ComboBox that contains an ObservableCollection.</p>
  
  <p>I want to add a "Please Select From List" to the top of the ComboBox. I tried using CompositeCollection to do this but could not get the ObservableCollection list to bind to the combobox, but the "Please Select" did bind OK.</p>
  
  <p>How can I add a "Please select" to the top of the ComboBox in this scenario? Does anyone have an example of this?</p>
  
  <p>Here is what I tried:
  XAML:</p>
  
  <pre><code>&lt;UserControl.Resources&gt;
      &lt;MyVM:MyViewModel x:Key="MyDataList"/&gt;
  &lt;/UserControl.Resources&gt;
  
  &lt;ComboBox....   
     &lt;ComboBox.ItemsSource&gt;
         &lt;CompositeCollection&gt;
              &lt;ComboBoxItem&gt;Select Address Type&lt;/ComboBoxItem&gt;
                    &lt;CollectionContainer Collection="{Binding Source={StaticResource MyDataList}}" /&gt;
         &lt;/CompositeCollection&gt;
     &lt;/ComboBox.ItemsSource&gt;
  </code></pre>