public void AddValidationResult(PendingPaymentValidationResult validationResult)
        {
            var existing = Model
                           .PendingPaymentValidationResultModels
                           .SingleOrDefault(v => v.Step.Equals(validationResult.Step) &&
                                            v.CollectionPeriod.AcademicYear == validationResult.CollectionPeriod.AcademicYear &&
                                            v.CollectionPeriod.PeriodNumber == validationResult.CollectionPeriod.PeriodNumber);

            if (existing != null)
            {
                Model.PendingPaymentValidationResultModels.Remove(existing);
            }

            Model.PendingPaymentValidationResultModels.Add(validationResult.GetModel());
        }