When will the custom description be used?

I took your code and tweaked it into a Country verifier for the Customer entity of NorthwindIB. Any subsequent attempt to set the Country property to null (regardless of the value of the Action property) elicited a generic "Country is required" message (not your custom message).

So I set a break point inside your VerifyValue() method and found that it never runs. The null check is simply resulting from the true setting on the second parameter of your call to the PropertyValueVerifierArgs constructor):


public IdentificationNumberRequiredVerifier()

: base ( new PropertyValueVerifierArgs<AccountMutation>(

IdentificationNumberEntityProperty.Name, true, "Identification Number"))

You can do just about anything with a delegate verifier. Here's one that makes the Title for an Employee required if the provided FirstName is less than two characters long.  (I modified the delegate verifier example from the Code Samples in the Validation topic.)

    #region Conditional Required Verifier

    private static Verifier TitleRequiredIfFirstNameIsShort() {
      string description = "A Title is required if the first name is shorter than two characters.";
      DelegateVerifier<Employee> v =
        new DelegateVerifier<Employee>(description, TitleRequiredCondition);
      v.AddTrigger(Employee.TitleEntityProperty.Name);
      v.ExecutionModes = VerifierExecutionModes.InstanceAndOnPostsetTriggers;
      return v;
    }

    private static VerifierResult TitleRequiredCondition(
      Employee pEmp, TriggerContext pTriggerContext,
      VerifierContext pVerifierContext) {

      if (pTriggerContext != null &&
        // We are not checking the proposed value because don't expect to call it preset
        pTriggerContext.Timing == TriggerTiming.Preset) {
        throw new VerifierException("TitleRequired verifier not implemented for Preset");
      }
      bool isValid = true;
      if (pEmp.FirstName.Length < 2 && pEmp.Title == null) {
        isValid = false;
      }
      return new VerifierResult(isValid);
    }

    #endregion