private void ShowAdButton_Click(object sender, System.EventArgs e)
 {
     // If no banner exists, show one; otherwise remove the existing one:
     if (bannerView == null)
     {
         // Optionally specify the banner’s anchor position:
         UnityBanners.SetBannerPosition(BannerPosition.BottomCenter);
         // Request ad content for your Placement, and load the banner:
         UnityBanners.LoadBanner(this, _placementId);
     }
     else
     {
         UnityBanners.Destroy();
         bannerView = null;
     }
 }
 public void LoadBanner()
 {
     // Request ad content for your Placement, and load the banner:
     UnityBanners.LoadBanner(this, _placementId);
 }