No, you can NOT use it while charging. Since this is a shaver that you can also use in the shower for wet shaving, Panasonic disabled this feature as a measure of safety. If you run out of battery you can quick charge it for 5 minutes, it should give you enough power for a complete shave.
Why would you want to use it with the cord attached? It charges incredibly fast. It has a digital display that shows remaining charge so you should not run out. If you do, plug it in and it will have sufficient charge for a complete shave in about 10 minutes.