Question

I have an array of zip codes. How do I obtain a list of every unique zip code in the array, and then count how many times the unique zip code occurred in the array?

I saw this:

A method to count occurrences in a list

I have a hunch this is the solution to my problem, but I don’t really understand it. Can someone please tell me if this is

1. indeed the best way to go about it. And
2. show me how to put an array into a List so that I can take advantage of GroupBy?

Answer 1

This should work for you:

var zips = new string[] { "12345", "12345", "54321" };
var groups = zips.GroupBy(z => z);

foreach(var group in groups)
    Console.WriteLine("{0} -> {1}", group.Key, group.Count());

Should give you:

12345 -> 2
54321 -> 1

driis actually gets you most of the way there. I just posted this to help show how to enumerate the groups.