title: Unity3D invalid token error on official code from documentation
body: <p>i was trying to set up simple ad system in my game in unity but the rewarded ads script from unity documentation is giving me invalid token error and i have no idea why</p>
  <pre><code>using UnityEngine;
  using UnityEngine.UI;
  using UnityEngine.Advertisements;
  
  public class RewardedAdsButton : MonoBehaviour, IUnityAdsLoadListener, IUnityAdsShowListener
  {
      [SerializeField] Button _showAdButton;
      [SerializeField] string _androidAdUnitId = &quot;Rewarded_Android&quot;;
      [SerializeField] string _iOSAdUnitId = &quot;Rewarded_iOS&quot;;
      public string _adUnitId = null;
  #if UNITY_IOS
          _adUnitId = _iOSAdUnitId;
  #elif UNITY_ANDROID
          _adUnitId = _androidAdUnitId;
  #endif
  </code></pre>
  <blockquote>
  <p>Assets\Scripts\RewardedAdsButton.cs(14,13): error CS1519: Invalid token '=' in class, struct, or interface member declaration</p>
  <p>Assets\Scripts\RewardedAdsButton.cs(14,31): error CS1519: Invalid token ';' in class, struct, or interface member declaration</p>
  </blockquote>