SAP Middleware Connector ArgumentException Collection was modified; enumeration operation may not execute

Question

I'm developing an application which uses an SAP.Middleware.Connector from SAP AG (version 3.0.2).

This application executes an RFC in the background (using Task.Run) but after a few minutes, the app crashes:

ArgumentException caught in DefaultDomain: Collection was modified; enumeration operation may not execute .
Uncaught Exception in DefaultDomain

Unhandled Exception: System.InvalidOperationException: Collection was modified; enumeration operation may not execute.
  at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
  at System.Collections.Generic.Dictionary'2.KeyCollection.Enumerator.MoveNext()
  at SAP.Middleware.Connector.RfcSessionManager.UpdateSessions(Object state)
  at System.Threading.TimerQueueTimer.CallCallbackInContext(Object state)
  at System.Threading.Executioncontext.RunInternal(ExecutionContext executionContext, ContextCallback, Object state, Boolean preserveSyncCtx)
  at System.Threading.Executioncontext.Run(ExecutionContext executionContext, ContextCallback, Object state, Boolean preserveSyncCtx)
  at System.Threading.TimerQueueTimer.CallCallback()
  at System.Threading.TimerQueueTimer.Fire()
  at System.Threading.TimerQueueTimer.FireNextTimers()
  at System.Threading.TimerQueueTimer.AppDomainTimerCallback()

This is the code of the RFC execution:

return Task.Run(() =>
ConexionSAP cSap = new ConexionSAP();
cSap.ConectaSAP();
RfcDestination rfcDest = RfcDestinationManager.GetDestination(cSap.rfc);
            
RfcRepository rfcRep = rfcDest.Repository;
IRfcFunction function;
function = rfcRep.CreateFunction("XXXNAMEOFTHEFUNCTIONXXX");

//import parameters
RfcSessionManager.BeginContext(rfcDest);
function.Invoke(rfcDest);

//export parameters
RfcSessionManager.EndContext(rfcDest);
});

Please, can you help please with this?

Answer 1

Thank you for your help!

I'm running on the answer of this. If you use BeginContext and EndContext on a Thread, the connector will try to renew the connection but now the thread containing the connection its gone causing the error, Collection was modified; enumeration operation may not execute.

The solution was to delete the BeginContext and EndContext line, everything is fine and working.