title: How to iterate through each of an element in a uwp page?
body: <p>I want to validate if any of the comboBoxes on the page have not been selected.</p>
  
  <p>I have tried:</p>
  
  <pre><code>foreach (ComboBox combo in PageName)
  {
      if (combo.SelectedIndex == -1)
      {
          // Activate Teaching Tip assosiated with this error to tell the user what needs changing
          NotSelected.IsOpen = true;
          return;
      }
  }
  </code></pre>
  
  <p>However it says 'PageName' is a type which isn't valid in the given context.</p>
  
  <p>Is there a way to achieve this?</p>