Collections in Depth

var list = new List<string>();       // ordered, duplicates allowed
var set = new HashSet<string>();      // unique elements
var dict = new Dictionary<string, int>(); // key -> value pairs

dict["Ada"] = 36;
dict["Grace"] = 85;
Console.WriteLine(dict["Ada"]);              // 36
Console.WriteLine(dict.ContainsKey("Bob"));  // false

foreach (var pair in dict) {
    Console.WriteLine($"{pair.Key} is {pair.Value}");
}

Directly parallel to Java's List/Set/Map: List<T> for order and duplicates, HashSet<T> for uniqueness, Dictionary<K, V> for key-based lookup.