Shopify Json construction before sending on the wire

gistfile1.txt

I need to construct the following JSON in C#, it will be sent on the wire afterwards:

{
  "custom_collection": {
    "title": "IPods",
    "collects": [
      {
        "product_id": 921728736
      }
    ]
  }
}

1. What is the most performant way to construct this?

2. How can one compose this with anonymous type construction? I had problem with the underscore separator within the key.

I'd like to avoid define all the "wrapper" classes with JsonProperty for the whole shopify API if possible.