! The story continues, Teo learns how the world functions in the future and finds a way to travel back in time. This is a detailed, deeper C# tutorial, which assumes that you have finished the 

Introduction to while loop

Introduction to methods

Repairing Noname

Introduction to arrays in C#

Lists

Introduction to scopes

Victory is close

Constants in C#

Wonderland

Input validation

Modulo operation

Career raise opportunity

Type conversion

Passing parameters to functions

Infinity

Switch statement

C# test

The truth

C# Intermediate

Learn the while loop; methods; arrays; scopes; constants; var keyword; math library in C#; type casts; ref and out modifiers; switch operator.

Intermediate course from Scratch for Absolute Beginners at CodeEasy Teaching Platform

When I was about to finish my conversation with a C gang guy, someone approached us. C gang guy immediately changed his face - he clearly didn't like the newcomer.

"This is Simon, from the gang that uses modern language features. We dislike them in our C gang." He whispered.

"Why, what did they do to you?" - I asked.

"They use high-level features that we don't have in C, but they exist in C#, Java, C++, and other modern languages. Just yesterday Simon tried to convince me that we should use dynamic arrays instead of the usual ones," the C gang guy replied.

"What do you mean, "dynamic arrays"? What is it?" - I asked.

"Ask him," he pointed at Simon, "he knows all these modern tricks. In C we don't have dynamic arrays and we live just fine!"

C gang guy pointedly spit in Simon's direction and left. Simon approached me and started talking. His voice sounded calm and friendly.

"Hi, there! I saw you around a couple of times, and it seems that you are getting under the C gang's influence. Don't dive too deep into those outdated concepts, let me show you some modern features of C#, so that you see how powerful this language is."

I didn't trust a single word of anyone in this cruel future world, but it seemed that this person can help me to grasp a new concept and he is not asking for anything in return, so let's give it a go.

"Today, I'll tell you about a type of dynamic array in C# called a list. A dynamic array is just an array that dynamically changes its size: it extends or shrinks when we need it." said Simon. He continued "In the past people were happy and naive. Instead of constantly looking for food (like we do), they were counting calories every day, to avoid eating to much. Can you believe this? Anyway, imagine we want to write a program that lets a person enter how many calories each meal of the day contains, what's the first step?"

I thought for a moment and replied "Well, I know that when we want to store multiple variables of the same type in a single variable we can use the array data structure! We should create an array to store the integers that the person enters for their calories''.

"Good thinking," Simon remarked, "but at the start of the day they don't know how many meals or snacks they will eat, and this is why we need to use a list! Let me explain"

 is used in C# to store multiple variables of the same type when you don't know how many elements are going to be needed. With a list you can also add and remove elements. A list has a lot more features than an array and you should use lists over arrays unless you have a good reason not to.

to the top of your code, in the "using" section. I will do it for you, so you don't need to bother.

said Simon, booting up his laptop and starting to write code.

"Ok, I'm following so far. The type of elements in the list goes inside the < > brackets, but how big is this list? What is its size?" I replied.

"When a list is created in this way its size is 0, it has no elements inside it at all. But 

to add an element, we can call a method on the list called 

"Ok, so if I've added those two numbers, just like an array, in memory it would be like this?" I asked.

"Exactly dude!" replied Simon, smiling. "And just like an array, if you know some of the values at creation you can make a new list like this:

This would be exactly the same as creating the list first and then adding the number 12 and 22 using the Add method."

"This all sounds very cool, but how do I read the values from the list?" I asked Simon.

"That's super easy, it's just like an array" said Simon typing more code on his laptop. "To read the values from the list you use the index of the cell"

"Now we know how to add items to our lists, let me tell you how we can remove things as well. This is where lists get really cool compared with arrays" exclaimed Simon excitedly.

"To remove an item in a list we can call the 

For example, here is a program where I create a list of the names of my favorite cars. If I want to remove "Fiat" from my list we call the Remove method, giving the item I want to remove as a parameter" said Simon showing me his laptop.

"We can even remove an item by specifying the index of the cell that we want to remove" continued Simon. "Check this out, here is a program that contains a list of drinks, if I wanted to remove water from the list, I know it's at index one so I can call the RemoveAt method passing the index of 1."

To remove an item from a list at a specific index, we call the RemoveAt method on the list and pass it the index of the cell that we want to be removed as a parameter.

 When we do this, all the cells to the right of the one that was removed shift to the left. For example: After we have called the RemoveAt method with the index of 1, milk stays in the same place but tea and coffee now shift left one space."

"When using arrays I like to use loops, I bet this works the same with lists?" I asked Simon confidently.

"Right again, kiddo! Just like with arrays we can use a 

 loop to access each item in a list. The only difference here is that 

with an array we use the 'length' property to get the size. But with a list we use the 'count' property to get the size 

. Let me show you"" Simon responded, working quickly on his laptop.

 in this case will be 3 because we have 3 items in our list" he continued.

"I pretty much never use for loops with lists, that is old school C-Gang-type thinking. In our gang we use 

 loops instead" said Simon smirking slightly. 

 loop you can still iterate over all items in a list 

but the code is faster to write and much nicer to read. You should pretty much always use a 

 loop with lists in C#," he continued as he turned to his laptop and showed me some code.

"Below are two examples of code that both achieve the exact same result. They iterate over a list and print out to the console the name of each breed of dog that is in the list.

In the for loop we create a string variable called "dog" and assign it to the element of the list which we are currently iterating, each time we go around the loop. We then print this out to the console.

 loop we don't need to create a variable called dog in the loop because the element we are currently iterating is automatically assigned to the variable of "dog" we declare in the 

"You seem to be understanding this really quickly, Teo," said Simon, clearly impressed. "Want to start learning some really cool things that lists can do?"

"When we use lists it's even possible to easily check if an item exists inside one of the cells! Check this out""

If we want to know if an element (cell) exists in a list we call the 

 method and pass a parameter of the item we want to check. The 

method will return a boolean value that is true if the item exists and false if not.

"That's really cool, you can do so much with lists," I told Simon.

"You've seen nothing yet, kid, check this out! There is even a modern language feature on lists that allows us to sort the values inside," said Simon.

on a list of numbers and the list will automatically be

"Woah! That's super impressive, but what happens if we call the sort method on list string?" I asked.

"That's a great question, Teal. Let me show you," replied Simon.

on a list of strings or characters and the list will automatically be

alphabetically ordered from smallest to largest

," said Simon. "Here, you try," he continued.

"I've got to shoot, you seem alright kid. Solve this task and we'll see if you really do understand lists in C#! Who knows if you get it right maybe one day you can join my gang!" said Simon as he walked away.

Learn best practices for dynamic arrays in C# - Lists