Adding CriterionUserInterest in a AdGroup returns CriterionError.CANNOT_ADD_CRITERIA_TYPE.

[art...@dinfo.com.br]

I'm using .NET Library and I trying add a user interest in a ad group, but I always receive the error CriterionError.CANNOT_ADD_CRITERIA_TYPE.

My code:

                CriterionUserInterest userInterestTarget = new CriterionUserInterest();

                userInterestTarget.userInterestId = interest.CriterionId;

                userInterestTarget.userInterestName = interest.Description;

                BiddableAdGroupCriterion interestBiddableAdGroupCriterion = new BiddableAdGroupCriterion();

                interestBiddableAdGroupCriterion.adGroupId = AdGroupId;

                interestBiddableAdGroupCriterion.criterion = userInterestTarget;

                AdGroupCriterionOperation interestBiddableAdGroupCriterionOperation = new AdGroupCriterionOperation();

                interestBiddableAdGroupCriterionOperation.operand = interestBiddableAdGroupCriterion;

                interestBiddableAdGroupCriterionOperation.@operator = Operator.ADD;

                _operations.Add(interestBiddableAdGroupCriterionOperation);

What am i doing wrong?