In build 2.08, we have added the option to register an event handler that receives workarea events. This can be used to monitor access to workareas and for example write this information to a log file.

 

There are two ways to install this event handler:

1.You create a function/ method that implements the DbNotifyEventHandler delegate:
 
PUBLIC DELEGATE XSharp.DbNotifyEventHandler(osender AS XSharp.RDD.IRDD, e AS XSharp.DBNotifyEventArgs) AS VOID
 

2.You create a class that implements the IDbnotify interface, which only has a method named Notify() with the same prototype as the delegate from 1)

Important

•Your event handler should do as little as possible if you don't want to slow down the whole RDD system.

•Do not manipulate any workareas from within your event handler to avoid recursion.

•Unregister your event handler as soon as possible.

•If you use an object for event handling, you are responsible yourself to manage the life time of this object. Also, be sure to unregister the object before it runs out of scope.

•In some cases (operations that work on more than one workarea, such as DbCommitAll() , DbUnLockAll() ),  the event handler will not always receive a sender parameter. Be prepared for that!

•The events are sent from the CoreDb level. So if a method inside an RDD calls another method inside that RDD (for example, CreateOrder() might call GoTop() after creating the order), you will not see that second event, only the events related to the method that was called from the CoreDb() level, so the events related to the Ordercreation in this example.

Examples

 

If you use approach 1, you need to add the event handler to CoreDb.Notify, like in the following example:

 

FUNCTION NotifyRDDOperations(oRDD AS XSharp.RDD.IRdd, oEvent AS XSharp.DbNotifyEventArgs) AS VOID
  IF oRDD != NULL
       ? oRDD:Alias, oEvent:Type:ToString(), oEvent:Data
  ELSE
       ? "(no area)",oEvent:Type:ToString(), oEvent:Data
  ENDIF
  RETURN
 
FUNCTION Start() AS VOID
  CoreDb.Notify += NotifyRDDOperations
   ? DbCreate("Test", {{"FLD1" , "C" , 10 , 0} })   // This will trigger a notification
 CoreDb.Notify -= NotifyRDDOperations                 // Do not forget to unregister!
  WAIT
RETURN

The parameters to the function are:

 

For the second approach you create a class. You can register the class with the DbRegisterClient() function and unregister the class with the DbUnRegisterClient function

The method in the class will get the same arguments as the event handler function:

CLASS Notifier IMPLEMENTS IDbnotify
    METHOD Notify(oRDD AS XSharp.RDD.IRdd, oEvent AS XSharp.DbNotifyEventArgs) AS VOID
      IF oRDD != NULL
         ? oRDD:Alias, oEvent:Type:ToString(), oEvent:Data
      ELSE
         ? "(no area)",oEvent:Type:ToString(), oEvent:Data
      ENDIF
      RETURN
END CLASS
 
FUNCTION Start() AS VOID
  LOCAL oNot AS Notifier
  oNot := Notifier{}
  DbRegisterClient(oNot)  
  ? DbCreate("Test", {{"FLD1" , "C" , 10 , 0} })   // This will trigger a notification
  DbUnRegisterClient(oNot)                                // Do not forget to unregister!
         
  WAIT
RETURN

See Also

DbNotificationType

DbRegisterClient()

DbUnRegisterClient

DbNotifyEventHandler

IDbnotify