C# Basic: From a javascript developer perspective

As a Junior developer, i've always been scared of learning 'Old' programming language that primarily uses OOP paradigm. However, today I decided to suck it up and at least try it. It isn't as bad as I think, there's similarities that it carries over to Javascript. Let us go through the basics first.

This blog assumes understanding of javascript

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The Basic

Data Types

Unlike javascript which is dynamically typed language, C# is statically typed language: The data type of a variable is known at the compile time which means the programmer has to specify the data type of a variable at the time of its declaration.

int: number (32bit)
decimal: number (128bit)
string: string
bool: Boolean
list[]: Array
dictionary{}: Object

-------------- Declaration ----------------
int myInt = 2147483647;
decimal myDecimal = 0.751m; // The m indicates it is a decimal
string myString = "Hello World"; // Notice the double-quotes
bool myBool = true;

List/Array

Note: You cannot add or extend the length if you use method 1 & 2
Declaring & assigning List method 1

string[] myGroceryArray = new string[2]; // 2 is the length
myGroceryArray[0] = "Guacamole";

Declaring & assigning List method 2

string[] mySecondGroceryArray = { "Apples", "Eggs" };

Declaring & assigning List method 3

List<string> myGroceryList = new List<string>() { "Milk", "Cheese" };
Console.WriteLine(myGroceryList[0]); //"Milk"
myGroceryList.Add("Oranges"); //Push new item to array

Declaring & assigning Multi-dimensional List

The number of ',' will determine the dimensions

string[,] myTwoDimensionalArray = new string[,] {
    { "Apples", "Eggs" },
    { "Milk", "Cheese" }
};

IEnumerable/Array

An array that is specifically used to enumerate or loop through.

You may ask, "What's the difference with list?". The answer is:

One important difference between IEnumerable and List (besides one being an interface and the other being a concrete class) is that IEnumerable is read-only and List is not.

List<string> myGroceryList = new List<string>() { "Milk", "Cheese" };

IEnumerable<string> myGroceryIEnumerable =  myGroceryList;

Dictionary/Object

Dictionary<string, string[]> myGroceryDictionary = new Dictionary<string, string[]>(){
    {"Dairy", new string[]{"Cheese", "Milk", "Eggs"}}
};

Console.WriteLine(myGroceryDictionary["Dairy"][2]);

Operators

Operators in C# behaves very similar to javascript so I won't describe it here

Conditionals

//Logic gate
  //There's no === in C#
myInt == mySecondInt 
myInt != mySecondInt 

myInt >= mySecondInt
myInt > mySecondInt
myInt <= mySecondInt 
myInt < mySecondInt 

// If Else
if () {}
else if () {}
else () {}

// Switch
switch (number)
{
    case 1:
        Console.WriteLine("lala");
        break;
    default:
        Console.WriteLine("default");
        break;
}

Loops

? Using foreach will be much faster than regular for loop

int[] intArr = new int[] { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

int totalValue = 0;

for (int i = 0; i < intArr.Length; i++)
{
    totalValue += intArr[i];
}

int forEachValue = 0;

foreach (int num in intArr)
{
    forEachValue += num;
}

Method

C# is first and foremost an OOP oriented language.

namespace HelloWorld
{
    internal class Program
    {
        static void Main()
        {
            int[] numArr = [1, 2, 3, 4, 5];
            int totalSum = GetSum(numArr);
        }

        static private int GetSum(int[] numArr)
        {
            int totalValue = 0;
            foreach (var item in numArr)
            {
                totalValue += item;
            }
            return totalValue;
        }
    }
}

Declaring Namespace & Model

Namespace is used to organization purpose, typically to organize classes

namespace HelloWorld.Models
{
    public class Computer
    {
        public string Motherboard { get; set; } = "";
        public int CPUCores { get; set; }
        public bool HasWIfi { get; set; }
        public bool HasLTE { get; set; }
        public DateTime ReleaseDate { get; set; }
        public decimal Price { get; set; }
        public string VideoCard { get; set; } = "";
    };
}

Starting C# 10, we can also declare namespace as such

namespace SampleNamespace;

class AnotherSampleClass
{
    public void AnotherSampleMethod()
    {
        System.Console.WriteLine(
            "SampleMethod inside SampleNamespace");
    }
}

Importing Namespace

using HelloWorld.Models;

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