You need to find a special item called an Up-Grade first, then trade your Porygon with another player whilst holding the Up-Grade to get a Porygon2.
evolve porygon from veilstone city
Porygon doesn't evolve at a level. You need a special item to make it evolve.
Just Evolve Porygon(1). And To Evolve Porygon(1),You Must Trade It.
To evolve Porygon to Porygon2, you will need to have it hold an Upgrade and trade it. You can get Porygon-Z by having Porygon hold a Dubious Disk and trade it.
trade while holding up grade and it will evolve into porygon 2
To evolve Porygon in Pokemon Platinum you need to trade it while it is holding the Up-Grade item. This will evolve Porygon into Porygon2. If Porygon2 is traded while holding a Dubious Disc it will evolve into Porygon-Z.
you have to have a upgrade and then trade it
In Pokemon Platinum, Porygon-2 can evolve into Porygon-Z using the Up-Grade. I do not believe it serves any other purposes.
For Porygon to evolve you have to trade it whilst it is holding an 'upgrade'. See related links for more info.
Have a Porygon hold it and trade it.When the other person gets it, it will evolve into a Porygon-2.
Trade it whilst its holding an Up-Grade
Try the GTS trick.