title: Databinding -- Reusing list, but different selecteditems
body: <p>I've got a datagrid with a structure like this:</p>
  
  <pre><code>Question 1  text question 1    &lt;pull down&gt;
  Question 2  text question 2    &lt;pull down&gt;
  Question 3  text question 3    &lt;pull down&gt;
  </code></pre>
  
  <p>The pull down comboboxes all have the same options: Yes, No, Maybe.
  Right now, I put the options in an observablecollection.</p>
  
  <p>My question is: How do I bind the selected item property of the combobox so that it pulls from a different object than the source observablecollection?</p>
  
  <p>Here's some code that might make it clearer what I'm trying to do</p>
  
  <pre><code>   public class ViewModel
     {
         ObservableCollection&lt;string&gt; options;
         ObservableCollection&lt;question&gt; questions;
     }
  
     public class question
     {
         public string selectedOption;
     }
  </code></pre>