WF 4.x Receive activity - TrackingParticipant & how to obtain the content parameters - workflow-foundation-4

Question

I am using WF 4.5 with a custom tracking system.
The tracking system will create task records in a custom database.
The tracking participant will create a task in the database whenever a Receive activity enters the 'Executing' state.
The tracking parcitipant will mark the task as completed in the database whenever a Receive activity enters the 'Closed' state.
When completing the task I need to fill in the user who executed the task.
The receive activity will have a custom class with a user property in it (content parameter).
I want to obtain this user property from the tracking participant.
How do I go about this?
public class WorkflowSystemTrackingParticipant : TrackingParticipant
{
protected override void Track(TrackingRecord record, TimeSpan timeout)
{
ActivityStateRecord aRecord = record as ActivityStateRecord;
... // get the parameters values send to the receive activity
}
}

Answer 1

Just like you track states and variables you want to track arguments also.
In your particular case you would track the InArgument<string> which holds the user you want.
new ActivityStateQuery
{
Variables = { * },
States = { "Executing", "Closed" },
Arguments = { "UserArgument" }
}
Now you can get the UserArgument which is available on ActivityStateRecord:
protected override void Track(TrackingRecord record, TimeSpan timeout)
{
var aRecord = record as ActivityStateRecord;
var userName = aRecord.Arguments["UserArgument"] as string;
// do whatever you want with 'username'
}