title: How to insert 'Empty' field in ComboBox bound to DataTable
body: <p>I have a combo box on a WinForms app in which an item may be selected, but it is not mandatory. I therefore need an 'Empty' first item to indicate that no value has been set.</p>
  
  <p>The combo box is bound to a DataTable being returned from a stored procedure (I offer no apologies for Hungarian notation on my UI controls :p ):</p>
  
  <pre><code> DataTable hierarchies = _database.GetAvailableHierarchies(cmbDataDefinition.SelectedValue.ToString()).Copy();//Calls SP
   cmbHierarchies.DataSource = hierarchies;
   cmbHierarchies.ValueMember = "guid";
   cmbHierarchies.DisplayMember = "ObjectLogicalName";
  </code></pre>
  
  <p>How can I  insert such an empty item?</p>
  
  <p>I do have access to change the SP, but I would really prefer not to 'pollute' it with UI logic.</p>
  
  <p><strong>Update:</strong> It was the DataTable.NewRow() that I had blanked on, thanks. I have upmodded you all (all 3 answers so far anyway). I am trying to get the Iterator pattern working before I decide on an 'answer'</p>
  
  <p><strong>Update:</strong> I think this edit puts me in Community Wiki land, I have decided not to specify a single answer, as they all have merit in context of their domains. Thanks for your collective input.</p>