private ValidationMessage BetweenLength( string value, int minLength, int maxLength, ValidationMessageType validationMessageType = ValidationMessageType.Error) { var betweenLengthValidator = new LengthValidator <TestValidatableObject>(_ => minLength, _ => maxLength, validationMessageType); var context = new ValidationContext <TestValidatableObject, string>(null, nameof(TestValidatableObject.Number), null, value); var validationMessage = betweenLengthValidator.ValidateProperty(context).FirstOrDefault(); return(validationMessage); }