title: How to set the value of a Gtk.ComboBox?
body: <p>All I can figure out is something to do with the ComboBox.GetEnumerator or something like that.</p>
  
  <p>I would like to do something like:</p>
  
  <pre><code>System.Collections.IEnumerator e = this.task_difficulty_combobox.GetEnumerator();
  while (e.MoveNext())
  {
      if (e.ToString() == this.task.Difficulty.ToString())
      {
          Gtk.TreeIter i = (Gtk.TreeIter)e.Current;
          this.task_difficulty_combobox.SetActiveIter(i);
          break;
      }
  }
  </code></pre>
  
  <p>However, This doesn't work.</p>