public void CreateInterstitialAd(string placementId, string channelId, string versionId)
{
this.interstitialClientPtr = (IntPtr)GCHandle.Alloc(this);
this.InterstitialPtr = YumiExterns.InitYumiInterstitial(this.interstitialClientPtr, placementId, channelId, versionId);
YumiExterns.SetInterstitiaCallbacks(
this.InterstitialPtr,
InterstitialDidReceiveAdCallback,
InterstitialDidFailToReceiveAdWithErrorCallback,
InterstitialDidClickCallback,
InterstitialDidCloseCallback);
}