Dispatcher m_Dispatcher = Dispatcher.CurrentDispatcher;       
EplApplication.LicenseRuntimeCheckCommands LicenseCallbackHandler(int nError, String strError, EplApplication.LicenseRuntimeCheckModes nLicenseRuntimeCheckMode)
{
   //we should be in the UI Thread.

   EplApplication.LicenseRuntimeCheckCommands response = EplApplication.LicenseRuntimeCheckCommands.Cancel;

   if (nLicenseRuntimeCheckMode == EplApplication.LicenseRuntimeCheckModes.TryCancel)
   {
       if (new Decider().Decide(EnumDecisionType.eYesNoDecision, "License error - Retry","",  EnumDecisionReturn.eYES, EnumDecisionReturn.eNO) == EnumDecisionReturn.eYES)
           response = EplApplication.LicenseRuntimeCheckCommands.Retry;
       else
           response = EplApplication.LicenseRuntimeCheckCommands.Cancel;
   }
   else if (nLicenseRuntimeCheckMode == EplApplication.LicenseRuntimeCheckModes.Cancel)
   {
       new Decider().Decide(EnumDecisionType.eOkDecision, strError, "License error - Cancel", EnumDecisionReturn.eOK, EnumDecisionReturn.eOK);
       response = EplApplication.LicenseRuntimeCheckCommands.Cancel;
   }

   return response;
}

delegate EplApplication.LicenseRuntimeCheckCommands LicenseCallbackHandlerDel(int nError, String strError, EplApplication.LicenseRuntimeCheckModes nLicenseRuntimeCheckMode);
EplApplication.LicenseRuntimeCheckCommands MyLicenseCallbackHandler(int nError, String strError, EplApplication.LicenseRuntimeCheckModes nLicenseRuntimeCheckMode)
{
   EplApplication.LicenseRuntimeCheckCommands response = EplApplication.LicenseRuntimeCheckCommands.Cancel;
  
   if (m_Dispatcher.CheckAccess())
   {
       //we are in the UI thread
       response = LicenseCallbackHandler(nError, strError, nLicenseRuntimeCheckMode);
   }
   else
   {
       //we are not in the UI thread, so we should switch to UI thread in order to use the UI control
       var obj = 
           m_Dispatcher.Invoke
               (                           
                   new LicenseCallbackHandlerDel(LicenseCallbackHandler),
                   new Object[] { nError, strError, nLicenseRuntimeCheckMode }
                   );

       response = (EplApplication.LicenseRuntimeCheckCommands)obj;
   }
  
   return response;
}