title: Modifying original DataSource doesn't update ComboBox
body: <p>I have a <code>ComboBox</code> with a <code>DataSource</code> set to application settings as follows</p>
  
  <pre><code>public DetailsForm()
  {
      InitializeComponent();
      this.comboBox1.DataSource = TextSelectionSettings.Default.categories;
  }
  </code></pre>
  
  <p>But I want users to add extra items to the combo box if they need to at runtime. So I just made a simple click event on a textbox to test adding a new string to the list.</p>
  
  <pre><code>private void textBox1_MouseClick(object sender, MouseEventArgs e)
  {
      TextSelectionSettings.Default.categories.Add("test");
      TextSelectionSettings.Default.Save();
  }
  </code></pre>
  
  <p>However the <code>ComboBox</code> doesn't show the new string I added to the settings.</p>
  
  <p>How can I refresh the <code>ComboBox</code> to show the changes in the settings?</p>
  
  <ul>
  <li><code>Refresh()</code> function on the combo box did not work.</li>
  <li>setting the <code>DataSource</code> again did not work either.</li>
  <li>I cannot add the <code>Item</code> directly to <code>ComboBox</code> using <code>Items.Add()</code> method because the <code>DataSource</code> is set.    </li>
  </ul>