/// <summary>
 /// Cancels an asynchronous request.
 /// </summary>
 public void Cancel(IOpcRequest request, TsCDaCancelCompleteEventHandler callback)
 {
     LicenseHandler.ValidateFeatures(LicenseHandler.ProductFeature.DataAccess);
     Subscription.Cancel(request, callback);
 }
 /// <summary>
 /// Cancels the request, if possible.
 /// </summary>
 public void Cancel(TsCDaCancelCompleteEventHandler callback)
 {
     subscription_.Cancel(this, callback);
 }
 /// <summary>
 /// Cancels an asynchronous request.
 /// </summary>
 public void Cancel(IOpcRequest request, TsCDaCancelCompleteEventHandler callback)
 {
     _subscription.Cancel(request, callback);
 }