how to use 10 overload of VerifierEngine.Execute


   i do this code :


        List<Verifier> verifiers = new List<Verifier>();

        verifiers.Add(GetPersonelUniqVerifier());

        VerifierContext pVerifierContext=new VerifierContext(VerifierOnErrorMode.Continue, ?) ;//I put null 
VerifierResultCollection results =
          mPersMgr.VerifierEngine.Execute(DetailInEdit, verifiers, pVerifierContext);//10 overload 


then run and tis error :
{"Object reference not set to an instance of an object."}
how to use 10 overload of how to use 10 overload of VerifierEngine.Execute


    public static Verifier GetPersonelUniqVerifier()
    {
        // ToDo: localize description
        string description = "کد پرسنلی نباید تکراری باشد.";
        DelegateVerifier<KarkardDetailTB> v =
          new DelegateVerifier<KarkardDetailTB>(description, PersonelUniqVerifierCondition);
        v.AddTriggers(Descriptors.MazayaID.Name);
        v.ExecutionModes = VerifierExecutionModes.InstanceAndOnPostsetTriggers;
        return v;
    }
    public static VerifierResult PersonelUniqVerifierCondition(
      KarkardDetailTB pMjd, 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("BornBeforeHired verifier not implemented for Preset");
        }
        if (pMjd.PersonID == KarkardDetailTB.GetPersonelID(pMjd.PersonID.Value,pMjd.KarkardID.Value))
            if (pMjd.Id != KarkardDetailTB.GetID(pMjd.PersonID.Value,0, false, pMjd.KarkardID.Value, KarkardTypeEnumTB.Mabani().EnumValue))
                return new VerifierResult(false);
        return new VerifierResult(true);
    }