Preface

This is aimed towards JavaScript developers who want to learn another programming language, or those who want to understand the process of learning something new in general.

I’m taking a course on edX titled Introduction to C#. I figured that it was about time I added another language to my arsenal. I’m going to compare what I learn about C# with JavaScript. I’ll comment on the similarities and the differences, rather than approach it from a brand-new coder’s perspective. Hopefully this review helps everyone out as much as it will help me out!

The Integrated Development Environment (IDE)

The course suggests that we use Visual Studio as our IDE for C# (pronounced C Sharp). I personally learned JavaScript using Visual Studio Code, which I believe is Visual Studio’s open-source younger brother. Visual Studio seems more robust and takes up way more space on your hard drive depending on what workloads you install. Workloads are basically add-ons that get automatically installed based on what kind of development you want to do (.NET, C++, Azure, Node, Office, etc.)

Data Types

The first thing we get into are the most commonly used C# value types (which are one of two data types.)

“Value types are so-called because they contain the actual value of the data they store.”

The ones JavaScript (JS) and C# share in common:
- JS Boolean() and C# bool
- string
Kind of similar:
- JS Date() vs. C# DateTime
- The JS number vs. C# int, long, float, double, and decimal
  
  To summarize the different C# number types briefly:
  - int is for whole numbers
  - long is for long whole numbers
  - float is for numbers with decimals
  - double is for numbers with lots more decimals
  - decimal is for if you need decimals (duh) and want to do exact/precise math (since float and double can result in some wonky math)
Unique to C#:
- char: Single character

There are more data types than what I’ve listed. A full list of C# data types can be found here.

Statements

int myVariable = 2;

This is a C# statement, which serves the same function as a JS statement. “Statements are formed from tokens. These tokens can be keywords, identifiers (variables), operators, and the statement terminator which is the semicolon (;). All statements in C# must be terminated with a semicolon.”

JavaScript

let myVariable = 2;

(Semicolon optional)

In JS, you don’t need to end everything with a semicolon, even though it is suggested. This is because JavaScript adds them in behind the scenes. It’s time to be a grown-up and put in those semicolons! With C#, ending statements with semicolons is a must, or it’ll throw an error (a nice red squiggly line will appear in Visual Studio).

These parts of the C# statement are tokens:

int, Data Type
myVariable, Variable
=, Assignment operator
2, Literal Value
;, Statement Terminator

Identifiers (Variables)

“In C#, an identifier is a name you give to the elements in your program.”

Identifier is a fancy word for variable. As examples, let’s look at those code snippets again:

int myVariable = 2;

When making a variable in C#, you must give it a data type (a lot of musts around here)! If you don’t, you’ll get an error. So we have to make myVariable into an int.

JavaScript

let myVariable = 2;

JS just uses let and myVariable automatically becomes a number because it sees that 2 is a number.

Some similarities for naming conventions:

Both languages have case-sensitive identifiers (myVar, _myVar, and myvar, are considered different identifiers).
Both can only contain letters, digits, and the underscore character (You cannot start the identifier with a digit. myVar and _myVar are legal but 2Vars is not).

Operators

“An operator is a token that applies to operations on one or more operands in an expression. An expression can be part of a statement, or the entire statement.”

Both languages share many of the same operators (+, -, *, /, %, etc.) The differences are left as an exercise for the reader.

Data Type Conversion

This is how you convert a data type into a different type in C#:

int myInt = 2147483647;
long myLong = myInt;

This is what is known as an implicit data conversion. “C# will use implicit conversion where it can, mostly in the case when a conversion will not result in a loss of data or when the conversion is possible with a compatible data type.”

In this example, converting an int to a long is fine because there is no data loss. The reverse, however, could result in data loss since long holds more data than int. In this case, we need to do explicit data conversion:

double myDouble = 1234.6;
int myInt;
// Cast double to int by placing the type modifier ahead of the type to be converted
// in parentheses
myInt = (int)myDouble;

double myDouble = 1234.6;
int myInt;
// Cast double to int by using the Convert class and the ToInt32() method.
// This converts the double value to a 32-bit signed integer
myInt = Convert.ToInt32(myDouble);

The first example uses () in front of the old variable to convert it into the type we put into the parentheses, (int)myDouble.

The second example uses a method provided by the .NET framework, Convert.ToInt32()

C# also gives us two more methods for casting types, TryParse() and Parse():

// TryParse() example
bool result = Int32.TryParse(value, out number);

// Parse() example
int number = Int32.Parse(value);

“In the TryParse() example, the method returns a Boolean result indicating if the conversion succeeded. In the Parse() example, if the conversion does not succeed, an exception will be thrown.”

Essentially, TryParse() tries to parse the value into the indicated data type, and it if works or not, it’ll tell you true or false. Parse() simply throws an error if it fails.

In JS, Number() converts to a Number, String() converts to a string, and Boolean() converts to a Boolean.

let myDouble = 1234.6;
let myInt;
myInt = myDouble;

Well, JS only has one numeric data type, so this^ code was kind of pointless…

Conventions

Like JS, C# enjoys the camel case convention, where the letter of each word is capitalized except the first, ex: camelCase or thisIsAnExampleVariable. It doesn’t matter too much, because each business has its own naming conventions that you’ll end up using.

Also, like JS, you can declare your variables in C# first before you assign values to them:

int myVariable = 2;
// OR
int myVariable;
myVariable = 2;

JavaScript

let myVariable = 2;
// OR
let myVariable;
myVariable = 2;

This also doesn’t matter too much; it’s a matter of preference.

Console.WriteLine() and other goodies

Console.WriteLine() is C#’s version of JS’s console.log. It’s similar to JS in the fact that you have to unintuitively space your strings out to make it look nice.

int age = 25;
Console.WriteLine("I am " + age + " years old.");

Output: I am 25 years old.

JavaScript

let age = 25;
console.log("I am " + age + " years old.");

Output: I am 25 years old.

Additionally, C# has a placeholder style for adding in variables using curly brackets:

int age = 25;
string city = "Oak Park";
Console.WriteLine("I am {0} years old and live in {1}.", age, city);