Collections and LINQ

using System.Linq;

List<int> scores = new List<int> { 80, 92, 67, 100 };

var passed = scores.Where(s => s >= 70).ToList();
var doubled = scores.Select(s => s * 2).ToList();
int total = scores.Sum();

Console.WriteLine($"passed: {string.Join(", ", passed)}");
Console.WriteLine($"total: {total}");

Collections

List<T> is a resizable, generic collection, the <int> says it only holds ints.

LINQ

LINQ (Language Integrated Query) adds query-style methods to collections, similar to JavaScript's map/filter/reduce:

LINQ methods live in the System.Linq namespace, and (like the JavaScript array methods they resemble) return a new sequence rather than modifying the original.