title: WPF combine two collections in one DataGrid
body: <p>I have two collections that I want to display together in one table. I intend to use a horizontal DataGrid for this, and I'm trying to figure out what the best way is to expose the collections to the DataGrid.
  (a horizontal DataGrid solution is described here: <a href="https://stackoverflow.com/questions/4132829/wpf-horizontal-datagrid">WPF horizontal DataGrid</a> )</p>
  
  <p>A bit of a nonsensical example with chairs and tables. In my application I have a list of tables and a list of chairs (both Table and a Chair have a Date and NumberOfItems property):</p>
  
  <pre><code>public List&lt;Table&gt; TableList { get; set; }
  public List&lt;Table&gt; ChairList { get; set; }
  </code></pre>
  
  <p>In xaml I want to DataBind to a combined list so that I would get something like:</p>
  
  <pre><code>Date             | 01-Jan-2011 | 02-Jan-2011 | 03-Jan-2011 | 04-Jan-2011 
  Number of tables |     5       |     6       |             |     7       
  Number of chairs |     3       |             |     2       |       
  </code></pre>
  
  <p>The TableList and ChairList do not have the same number of items. 
  What would be the best approach to expose a bindable combined collection?</p>