HashSet<int> validStoryPointValues = new HashSet<int>() { 1, 2, 3, 5, 8, 13, 21 };
bool containsEight = validStoryPointValues.Contains(8); // O(1)

List<int> validStoryPointValues = new List<int>() { 1, 2, 3, 5, 8, 13, 21 };
bool containsEight = validStoryPointValues.Contains(8); // O(n)

using System.Collections.Generic;

var people = new Dictionary<string, int>
{
    { "John", 30 }, {"Mary", 35}, {"Jack", 40}
};

// Reading data
Console.WriteLine(people["John"]); // 30
Console.WriteLine(people["George"]); // throws KeyNotFoundException

int age;
if (people.TryGetValue("Mary", out age))
{ 
    Console.WriteLine(age); // 35
}

// Adding and changing data
people["John"] = 40;    // Overwriting values this way is ok
people.Add("John", 40); // Throws ArgumentException since "John" already exists

// Iterating through contents
foreach(KeyValuePair<string, int> person in people)
{
    Console.WriteLine("Name={0}, Age={1}", person.Key, person.Value);
}

foreach(string name in people.Keys)
{
    Console.WriteLine("Name={0}", name);
}

foreach(int age in people.Values)
{
    Console.WriteLine("Age={0}", age);
}

var people = new Dictionary<string, int>
{
    { "John", 30 }, {"Mary", 35}, {"Jack", 40}, {"Jack", 40}
}; // throws ArgumentException since "Jack" already exists

// create an empty set
var mySet = new SortedSet<int>();

// add something
// note that we add 2 before we add 1
mySet.Add(2);
mySet.Add(1);

// enumerate through the set
foreach(var item in mySet)
{
    Console.WriteLine(item);
}

// output:
// 1
// 2

// create an array with 2 elements
var myArray = new [] { "one", "two" };

// enumerate through the array
foreach(var item in myArray)
{
    Console.WriteLine(item);
}

// output:
// one
// two

// exchange the element on the first position
// note that all collections start with the index 0
myArray[0] = "something else";


// enumerate through the array again
foreach(var item in myArray)
{
    Console.WriteLine(item);
}

// output:
// something else
// two

using System.Collections.Generic;

var list = new List<int>() { 1, 2, 3, 4, 5 };
list.Add(6);
Console.WriteLine(list.Count); // 6
list.RemoveAt(3);
Console.WriteLine(list.Count); // 5
Console.WriteLine(list[3]);    // 5

// Initialize a stack object of integers
var stack = new Stack<int>(); 

// add some data
stack.Push(3);
stack.Push(5);
stack.Push(8);

// elements are stored with "first in, last out" order.
// stack from top to bottom is: 8, 5, 3

// We can use peek to see the top element of the stack.
Console.WriteLine(stack.Peek()); // prints 8

// Pop removes the top element of the stack and returns it.
Console.WriteLine(stack.Pop()); // prints 8
Console.WriteLine(stack.Pop()); // prints 5
Console.WriteLine(stack.Pop()); // prints 3

// initialize a LinkedList of integers
LinkedList list = new LinkedList<int>();

// add some numbers to our list.
list.AddLast(3);
list.AddLast(5);
list.AddLast(8);

// the list currently is 3, 5, 8

list.AddFirst(2);
// the list now is 2, 3, 5, 8

list.RemoveFirst();
// the list is now 3, 5, 8

list.RemoveLast();
// the list is now 3, 5

// Initalize a new queue of integers
var queue = new Queue<int>();

// Add some data
queue.Enqueue(6);
queue.Enqueue(4);
queue.Enqueue(9);

// Elements in a queue are stored in "first in, first out" order.
// The queue from first to last is: 6, 4, 9

// View the next element in the queue, without removing it.
Console.WriteLine(queue.Peek()); // prints 6

// Removes the first element in the queue, and returns it.
Console.WriteLine(queue.Dequeue()); // prints 6
Console.WriteLine(queue.Dequeue()); // prints 4
Console.WriteLine(queue.Dequeue()); // prints 9