title: Add Items to ComboBox from an IEnumerable object
body: <p>I have a <code>System.Timers.Timer</code> that updates my win form application components in every 5 seconds.</p>
  
  <p>I have a comboBox and global <code>IEnumerable&lt;Person&gt;</code> list that updated also in everty 5 seconds.
  I need to add persons name to combobox. If the name is already in the list, i should not add.</p>
  
  <p>How can I proceed?
  Here is the code inside the timer event. This adds multiple times and i am not sure to do that with <code>foreach,</code> maybe <code>IEnumareble</code> interface has an easier way.</p>
  
  <pre><code>foreach (Persons person in personsList)
  {
    comboBox.Items.Add(person.Name);
  }
  </code></pre>