title: DataTable Item array not assigning
body: <p>I am reading in an XML file into a Dataset, then adding a new column, then assigning a value to each row in that column.</p>
  
  <p>My program creates the new column and I can see that it has the BitmapImage datatype by looking at it in the debug screen while its running and using a messagebox to toString its datatype.</p>
  
  <p>But when i try to assign something to that row's column, it remains as '{}' and when I attempt to use it it gives the the error 'Unable to cast type DBNull to BitmapImage';</p>
  
  <pre><code>ItemDS = new DataSet();
  ItemDS.ReadXml(homeFolder + @"Items.xml", XmlReadMode.InferSchema);
  ItemDS.Tables[0].Columns.Add("pic", typeof(BitmapImage));
  MessageBox.Show(ItemDS.Tables[0].Columns[5].DataType.ToString());
  foreach (DataRow theRow in ItemDS.Tables[0].Rows)
  {
      try
      {
          theRow.ItemArray[5] = (SquareImageFromFile(NewDeployFolder + @"assets\images\items\" + theRow.ItemArray[3].ToString(), 120));
      }
      catch (Exception ex)
      {
          MessageBox.Show(ex.ToString());
      }
      combItem.Items.Add(theRow.ItemArray[0]);
  }
  </code></pre>
  
  <p>When I run the assignment row, no error comes up, but nothing happens to the item array after the line is run.</p>