Using File Server Handle provided by Application Framework.
The Control Environment (CONE), which forms part of the application framework for UI applications, provides a permanent handle to the File Server to help reduce the number of connected File Server Sessions needed.
You don’t need to open a file server session, since the control environment already has an open RFs, to access it, we need to invoke FsSession() on the iCoeEnv member of the View class.
RFs aFs = iCoeEnv->FsSession();
iErr = file.Open(aFs,aFilename,EFileRead) ;
if( iErr == KErrNone)
// Do Something...