From what I can see - there is no strong typing on Veggie pizza...

[computamike]

The pre-made pizza (beef lovers pizza for example) are collections of strings as their toppings, whereas there nothing preventing a person from putting anchovies onto a veggie pizza, or as part of the 'recipe'

so - for instance

{ "Meat Lovers", new[] { "pepperoni", "beef", "sausage", "ham", "Soilent Green"} },

is a technically correct, because a meat pizza is a Lazy<Dictionary<string, string[]> whereas it should probably be :

Lazy<Dictionary<string, _meats[]>
(not sure of syntax here)

Perhaps these should be refactored, so that a pizza has a list of toppings of a type, preventing a shop from offering a veggie pizza with accidental meat. If should also mean that from a type safety point of view that it wouldn't be possible to add an ingredient to a pizza without it existing already in the Meat / veggies type.

[javajudt]

Good point. Part of why I implemented it this way is because the response that Alexa speaks comes directly from the array of strings. It was simple to implement it this way because I could just do a string.Join() and inject directly into the OutputSpeech. But your idea leads to more robust code. I think it's similar to #30 that I just opened.