Business Processor: Unable to reference a property in the 'request' object

I am creating a BPL using the Management Portal instead of creating a custom class. 

As per the documentations 'request object' contains properties those were in the original request message object or primary request and can be reference using the dot syntax. 

So if the primary request was an HL7 message, i should be able to pull the value MSH:9.2 as  follow 

request.{MSH:9.2} and assign it to a context property

attached image is a screen shot of my configuration, set  context.X  to request.{MSH.MessageType.triggerevent} i have also tried referencing the object property by number instead of name set  context.X  to request.{MSH.9.2} 

But i am getting this error 

18:17:50.204:Ens.Actor: ERROR <Ens>ErrBPTerminated: Terminating BP ProcessPIDSegment # due to error: ERROR <Ens>ErrException: <PROPERTY DOES NOT EXIST>zS1+2^TestFarhad.BlastAMessageBasedOnPID3.Thread1.1 *source,EnsLib.HL7.Message -- logged as '-' number - @' Set status=1,context.X=request.source.GetValueAt("MSH:MessageType.triggerevent")'

17:54:26.384:Ens.Actor: ERROR <Ens>ErrBPTerminated: Terminating BP ProcessPIDSegment # due to error: ERROR <Ens>ErrException: <INVALID OREF>zS1+2^TestFarhad.BlastAMessageBasedOnPID3.Thread1.1 -- logged as '-' number - @' Set status=1,context.X=request.GetValueAt("MSH:9.2")'

I have verified message contain a value in MSH:9.2, sample message is below

MSH|^~\&|QCPR|JA|||201707251356||ADT^A31|6960|T|2.3||||||pt updt (no visit)|
EVN|A31|201707251356||||
PID|1||111111^^^^MR^JA~2222^^^^MR^NO||Novus^Inpatient^^^||19720418|M||Black or African American|99 Nightfall Avenue^63^Bronx^NY^10457^U.S.A.|Bronx||^^^||Divorced|Catholic|||||||||||||
PD1||||||||||||N||

just for concept testing i have assigned the context.X property to a string and then displayed the string and it does populate. 

Can you please assist with how should i reference any property in the HL7 messages using the request object. 

Thank You