In this part of my C# tutorial we’ll explore many collections available with C#. We’ll look at ArrayLists, Dictionaries, Queues, and Stacks. We’ll test out most every function available with them.

For best results take notes on the heavily commented code provided below as you watch and leave any questions you have. This is the book students tell me is the best for learning C#.

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Code & Transcript

using System;
using System.Linq;

// Used for ArrayLists
using System.Collections;

// Used for Dictionary
using System.Collections.Generic;

namespace CSharpTutA.cs
{
    class Program
    {
        static void Main(string[] args)
        {
            // Collections can resize unlike arrays

            // #region provides a way to collapse
            // long blocks of code

            // ---------- ARRAYLISTS ----------
            #region ArrayList Code

            // ArrayLists are resizable arrays
            // that can hold multiple data types
            ArrayList aList = new ArrayList();

            aList.Add("Bob");
            aList.Add(40);

            // Number of items in list
            Console.WriteLine("Count: {0}",
                aList.Count);

            // The capacity automatically increases
            // as items are added
            Console.WriteLine("Capacity: {0}",
                aList.Capacity);

            ArrayList aList2 = new ArrayList();

            // Add an object array
            aList2.AddRange(new object[] { "Mike", "Sally", "Egg" });

            // Add 1 array list to another
            aList.AddRange(aList2);

            // You can sort the list if the types 
            // are the same
            aList2.Sort();
            aList2.Reverse();

            // Insert at the 2nd position
            aList2.Insert(1, "Turkey");

            // Get the 1st 2 items
            ArrayList range = aList2.GetRange(0, 2);

            /*
            // Remove the first item
            aList2.RemoveAt(0);

            // Remove the 1st 2 items
            aList2.RemoveRange(0, 2);
            */

            // Search for a match starting at the provided 
            // index. You can also find the last index
            // with LastIndexOf
            Console.WriteLine("Turkey Index : {0}",
                aList2.IndexOf("Turkey", 0)); 

            // Cycle through the list
            foreach (object o in range)
            {
                Console.WriteLine(o);
            }

            // Convert an ArrayList into a string array
            string[] myArray = (string[])aList2.ToArray(typeof(string));

            // Convert a string array into an ArrayList
            string[] customers = { "Bob", "Sally", "Sue" };
            ArrayList custArrayList = new ArrayList();
            custArrayList.AddRange(customers);

            #endregion


            // ---------- DICTIONARIES ----------
            #region Dictionary Code

            // Dictionaries store key value pairs
            // To create them define the data
            // type for the key and the value
            Dictionary<string, string> superheroes = new Dictionary<string, string>();

            superheroes.Add("Clark Kent", "Superman");
            superheroes.Add("Bruce Wayne", "Batman");
            superheroes.Add("Barry West", "Flash");

            // Remove a key / value
            superheroes.Remove("Barry West");

            // Number of keys
            Console.WriteLine("Count : {0}",
                superheroes.Count);

            // Check if a key is present
            Console.WriteLine("Clark Kent : {0}",
                superheroes.ContainsKey("Clark Kent"));

            // Get the value for the key and store it
            // in a string

            superheroes.TryGetValue("Clark Kent", out string test);

            Console.WriteLine($"Clark Kent : {test}");

            // Cycle through key value pairs
            foreach(KeyValuePair<string, string> item in superheroes)
            {
                Console.WriteLine("{0} : {1}", 
                    item.Key,
                    item.Value);
            }

            // Clear a dictionary
            superheroes.Clear();


            #endregion

            // ---------- QUEUES ----------
            #region Queue Code
            // Queue 1st in 1st Out Collection

            // Create a Queue
            Queue queue = new Queue();

            // Add values
            queue.Enqueue(1);
            queue.Enqueue(2);
            queue.Enqueue(3);

            // Is item in queue
            Console.WriteLine("1 in Queue : {0}",
                queue.Contains(1));

            // Remove 1st item from queue
            Console.WriteLine("Remove 1 : {0}",
                queue.Dequeue());

            // Look at 1st item but don't remove
            Console.WriteLine("Peek 1 : {0}",
                queue.Peek());

            // Copy queue to array
            object[] numArray = queue.ToArray();

            // Print array
            Console.WriteLine(string.Join(",", numArray));

            // Print queue items
            foreach (object o in queue)
            {
                Console.WriteLine($"Queue : {o}");
            }

            // Clear the queue
            queue.Clear();


            #endregion

            // ---------- STACKS ----------
            #region Queue Code
            // Stack Last in 1st Out Collection

            // Create a stack
            Stack stack = new Stack();

            // Put items on the stack
            stack.Push(1);
            stack.Push(2);
            stack.Push(3);

            // Get but don't remove item
            Console.WriteLine("Peek 1 : {0}",
                stack.Peek());

            // Remove item
            Console.WriteLine("Pop 1 : {0}",
                stack.Pop());

            // Does item exist on stack
            Console.WriteLine("Contain 1 : {0}",
                stack.Contains(1));

            // Copy stack to array
            object[] numArray2 = stack.ToArray();

            // Print array
            Console.WriteLine(string.Join(",", numArray2));

            // Print the stack
            foreach (object o in stack)
            {
                Console.WriteLine($"Stack : {o}");
            }

            // Clear stack

            #endregion

            Console.ReadLine();

        }
        
    }

}