The ProcessPIUser property of the LogMessage2 object is a Read-Only string that represents the authenticated PI user associated with a message being logged.
The MessageLog2.SendLogMessage method will automatically add the ProcessPIUser to any log message sent to a PI server's Message log (remote messages). When sending messages to the local log the PI-SDK can not determine the proper PI user so this property is not added automatically though can be explicitly sent by an application. If an application is doing work on behalf of a PI User not associated with the server connection being used to log a message, the OriginatingPIUser message property should instead be sent.
The object placeholder is an object expression that evaluates to a LogMessage2 object.