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()); }