Global-like data in C#

Hmm... well, you can have a "Game State" object, for example. This object would hold the other objects that constitute the Map etc...

Then in the main routine, initialize an instance of the Game State object. Essentially it's probably similar to the singleton notion, but sometimes when you need data you need data.

From there, you could do a few things. You could pass any other objects that need to know about the Game State a reference to said object. You could also set up an Observer/Observable pattern where objects that just need to know when the game state changes are informed when changes occur.

Hopefully that helps... personally though, I say do what you understand. Sometimes following the rules of OO Programming can lead to solutions that, while much easier to maintain, are less efficient: and if it's a private project, you may not have to worry as much about said maintenance.

I don't know if it would be a problem, but the gamestate would be huge, containing the map and some even more elaborate data.

I don't actually find passing the parameters to be inelegant, but I worry about overhead. Since I'm not actually using the data passed for more than lookups and such in most cases, can I pass by reference and then stop worrying about the memory usage and such?

When dealing with reference types, there's no more overhead to passing around a large object than a small one. This is because you're passing around the reference to it, not the object itself. A reference to a big object is the same size as a reference to a small one.

So make sure it's a class, and not a struct, and pass it to the constructors of any class that uses it.