Auto Air Conditioning & Heater Repair: a/c not taking refrigerant, orifice tube, atmospheric air

Question
I replaced the dryer on my vehicle.  I have the service manual, and a set of gauges, however a number of people have told me I do not need to evacuate the system prior to recharge.  The system only took on can of refrigerant.  I suspect that they are wrong and I do need to evacuate the system.  Can you confirm?

Answer
Of course you have to evacuate all the atmospheric air from out of the system BEFORE you can recharge it.

I STRONGLY suggest that you replace the orifice tube or expansion valve, whichever you particular vehicle happens to utilize as they collect debris from the ac system over the years and plug up.

WHY did you replace the dryer ?. Just curious.