4.3 List

The difference between a list and an array is that lists are dynamic, while arrays have a fixed size. When you do not know the amount of variables your array should hold, use a list instead.

File Location

1. Right click on your solution

2. Go to Add > New Project and select Console App (.NET Framework)

3. Name it Lists

Visualization

 class Program
    {
        static void Main(string[] args)
        {
//          1     2     3         4
            List<int> numbers = new List<int>();
//          5 
            numbers.Add(1);
            numbers.Add(2);
            numbers.Add(3);
        }
    }

1. Declaring that you are building a list

2. The datatype your list will hold

3. The name of your list

4. Initializing a new list

5. Adding values to your list using the function .Add()

Initializing a List

A List can be initialized with a variable of List<int>;. List can use any of the data types used within C#. Then you go on to name your list and instantiate it. It should look something like this:

List<int> numbers = new List<int>();

Adding Values To Your List

We use an Add() method after the list's name to add values into a list.

 class Program
    {
        static void Main(string[] args)
        {
            List<int> numbers = new List<int>();
            numbers.Add(1);
            numbers.Add(2);
            numbers.Add(3);
        }
    }

You can also add a whole array to a list using the AddRange function.

 class Program
    {
        static void Main(string[] args)
        {
            List<int> numbers = new List<int>();
            int[] array = new int[] { 1, 2, 3 };
            numbers.AddRange(array);
        }
    }

Removing From a List

We can use Remove() to remove an item from a list by specifying the item we want to remove.

 class Program
    {
        static void Main(string[] args)
        {
            List<string> fruits = new List<string>();
            // add fruits
            fruits.Add("apple");
            fruits.Add("banana");
            fruits.Add("orange");

            // now remove the banana
            fruits.Remove("banana");
            Console.WriteLine(fruits.Count);
        }
    }

We can also use RemoveAt() to specify an index of an item to remove. In our case, to remove the banana, we will use the index 1.

 class Program
    {
        static void Main(string[] args)
        {
            List<string> fruits = new List<string>();
            // add fruits
            fruits.Add("apple");
            fruits.Add("banana");
            fruits.Add("orange");

            // now remove the banana
            fruits.RemoveAt(1);
            Console.WriteLine(fruits.Count);
        }
    }

Concatenating Lists

 class Program
    {
        static void Main(string[] args)
        {
            List<string> food = new List<string>();
            food.Add("apple");
            food.Add("banana");

            List<string> vegetables = new List<string>();
            vegetables.Add("tomato");
            vegetables.Add("carrot");

            food.AddRange(vegetables);
            Console.WriteLine(food.Count);
        }
    }

Challenge

Bronze Challenge

• Use the C# List type to make a string list of 10 phone numbers

• Make the numbers 317.555.0001 all the way up to 317.555.0010

• Print the 10 numbers to the console by ITERATING over the list

Silver Challenge

• Let's pretend that Paul's phone number is 317.555.0005

• Loop through the list and print that number with the message "Paul's phone number is 317.555.0005

• Do the same with another person's number, except theirs ends with 0007

  Answers

  Next: More about OOP