tModLoader Spawn NPC from an instance as opposed to using an ID.

[Etotheipi]

Say I had an npc class called MyNPC. The way I think this is done is with the NPC.NewNPC(x, y, id) method. However using that method doesn't let you edit any fields before you summon it. So I was wondering if I had code like the following,

MyNPC myNpc = new MyNPC();
myNpc.randomField = 17;

How could I spawn myNpc into the world?