How to retrieve a list of checkboxes selected among all those of the form?

I have about 20 checkbox's on the GUI I'm working on and depending on which ones are checked, determines the inputs I need.

I know how to check if a checkbox is checked or not, and can determine the inputs that way.

But I don't want to do that for all 20+ checkbox's.

Is there a way to get the checked checkboxes?

Something like:

string[] ports = new string[3];
ports[] = list_of_checkboxs_that_are_checked;

And then just limit the user to only selecting 3, or however many?