CSharp (C#) Language Reference

01/02/2020 Off By Learners Heaven

C# pronounce as C Sharp is a one of the best and powerful Object Oriented Programming language. Created by Microsoft first released in year 2002. C# Require .Net Framework Runtime. Till now 8.0 is the latest version of C#.

C# is the best programming language for Console, Web, Desktop and Mobile application development. Now Microsoft also released .Net Core Framework for cross platform support. So C# runs also on Mac OS and Linux.

In this article we will learn following things of C#

01. C# Syntax
02. C# Comments
03. C# Keywords
04. C# Variables & Data Types
05. C# Type Casting
06. C# User Input
07. C# Operators
08. C# Special Characters & preprocessor directives
09. C# Strings
10. C# Conditional Statement if .. else
11. C# Switch statement
12. C# Loops
13. break/continue
14. Array

01. C# Syntax

Minimum code block for running a C# application is given below

using System;

namespace HelloWorld
  class Program
    static void Main(string[] args)
      Console.WriteLine("Hello World!");    

Code analysis line by line

1:  using System; 
// is used for importing builtin library functionalities. Here also we can import namespace of our class libraries.

3:  namespace HelloWorld 
// namespace groups multiple class into a single group so that if we include that namespace into top of our code with using keyword then it includes all class library of that namespace.

4: { .. } 
//curly braces {} marks the beginning and the end of a block of code.

5: class HelloWorld 
// C# is a Object Oriented Programming language. So we must write our method/function inside a class always. 

7: static void Main(string[] args) 
//Every C# program has static Main method. Application starts from that method. 
9: Console.WriteLine("Hello World!");  
//Will print Hello World! at black console window. 

02. C# Comments

Two types of commenting system is supported by c#. Single line comment and multi line comment. Commented line does not execute.

Single line comment start with double front slash //

Multi Line comment starts with /* and ends with */


// This is an example of single line comment
//Console.WriteLine("Hello World");

Multi Line comment example
var url = "https://learnersheaven.com";
var html = WebClient.DownloadText(url);
var webClient = new System.Net.WebClient();
var html = webClient.DownloadString("https://learnersheaven.com");

03. C# Keywords

usingusing staticvirtualvoid

Contextual keywords

orderbypartial (type)partial (method)
unmanaged (generic type constraint)valuevar
when (filter condition)where (generic type constraint)where (query clause)

Details uses of each keyword we will learn at another article.

04. C# Variables & Data Types

Variables are containers for storing different types of data. C# supports following primitive data types

int - stores integers (whole numbers), without decimals, such as 103 or -103
double - stores floating point numbers, with decimals, such as 10.99 or -20.99
char - stores single characters, such as 'a' or 'B'. Char values are surrounded by single quotes
string - stores text, such as "Hello World". 
bool - stores values with two states: true or false

Variable deceleration syntax

Data type then variable name. If we want to initialize then have to set value by using assignment operator =

int totalValue = 10;
double sum = 20.50;
char firstChar = 'A';
string firstName = "Learners";
bool isDone = true;

Size of Data Type

Data Type Size Description
int 4 bytes Stores whole numbers from -2,147,483,648 to 2,147,483,647
long 8 bytes Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
float 4 bytes Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits
double 8 bytes Stores fractional numbers. Sufficient for storing 15 decimal digits
bool 1 bit Stores true or false values
char 2 bytes Stores a single character/letter, surrounded by single quotes
string 2 bytes per character Stores a sequence of characters, surrounded by double quotes

05. C# Type Casting

Type casting is required when we want to assign a value of one data type to another type. C# supports two types of type casting.

  • Implicit Casting (automatically) – converting a smaller type to a larger type size char -> int -> long -> float -> double


int myInt = 12;
double myDouble = myInt;       // Automatic casting: int to double
Console.WriteLine(myInt);      // Outputs 12
Console.WriteLine(myDouble);   // Outputs 12
  • Explicit Casting (manually) – converting a larger type to a smaller size type double -> float -> long -> int -> char


double myDouble = 10.78;
int myInt = (int) myDouble;  // Manual casting: double to int
Console.WriteLine(myDouble); // Output 10.78
Console.WriteLine(myInt);    // Output 10

06. C# User Input

We have already learned that Console.WriteLine() is used to output (print) values. Now we will use Console.ReadLine() to get user input.

/* String input */
// Type your username and press enter
Console.WriteLine("Enter username:");
// Create a string variable and get user input from the keyboard and store it in the variable
string userName = Console.ReadLine();
// Print the value of the variable (userName), which will display the input value
Console.WriteLine("Username is: " + userName);

/* Number input */
Console.WriteLine("Enter your age:");
int age = Convert.ToInt32(Console.ReadLine());
Console.WriteLine("Your age is: " + age);

07. C# Operators

Operators are used to perform operations on variables and values. In the example below, we use the + o add together two values:

int x = 100 + 50;        // 150 (100 + 50)
int sum1 = x + 250;      // 400 (150 + 250)
int sum2 = x + sum1;     // 800 (400 + 400)

C# Arithmetic Operators

Arithmetic operators are used to perform common mathematical operations:

Operator Name Description
+ Addition Adds together two values
Subtraction Subtracts one value from another
* Multiplication Multiplies two values
/ Division Divides one value from another
% Modulus Returns the division remainder
++ Increment Increases the value of a variable by 1
Decrement Decreases the value of a variable by 1

C# Assignment operators

OperatorExampleSame As
=x = 5x = 5
+=x += 3x = x + 3
-=x -= 3x = x – 3
*=x *= 3x = x * 3
/=x /= 3x = x / 3
%=x %= 3x = x % 3
&=x &= 3x = x & 3
|=x |= 3x = x | 3
^=x ^= 3x = x ^ 3
>>=x >>= 3x = x >> 3
<<=x <<= 3x = x << 3

C# Comparison Operators

Operator Name Example
== Equal to x == y
!= Not equal x != y
> Greater than x > y
< Less than x < y
>= Greater than or equal to x >= y
<= Less than or equal to x <= y

C# Logical Operators

Operator Name Description Example
&&  Logical and Returns true if both statements are true x < 5 &&  x < 10
||  Logical or Returns true if one of the statements is true x < 5 || x < 4
! Logical not Reverse the result, returns false if the result is true !(x < 5 && x < 10)

08. C# Special Characters & preprocessor directives

Special characters are predefined, contextual characters that modify the program element (a literal string, an identifier, or an attribute name) to which they are prepended. C# supports the following special characters:

  • @, the verbatim identifier character.
  • $, the interpolated string character.

Preprocessor directives













#pragma warning

#pragma checksum

09. C# Strings

Strings are used for storing text.

string variable contains a collection of characters surrounded by double quotes:

string txt = "Hello World";
Console.WriteLine(txt.ToUpper());   // Outputs "HELLO WORLD"
Console.WriteLine(txt.ToLower());   // Outputs "hello world"

//String Concatenation
string firstName = "John ";
string lastName = "Wick";
string name = firstName + lastName;
Console.WriteLine(name);  // Outputs John Wick

//String Interpolation
string firstName = "John";
string lastName = "Wick";
string name = $"My full name is: {firstName} {lastName}";
Console.WriteLine(name); // Outputs My full name is: John Wick

// Special Characters inside string
// Special characters are used inside a string after a back slash \
string txt = "We are learning \"C#\" at learnersheaven.com";

10. C# Conditional Statement if .. else

C# supports the usual logical conditions from mathematics:

  • Less than: a < b
  • Less than or equal to: a <= b
  • Greater than: a > b
  • Greater than or equal to: a >= b
  • Equal to a == b
  • Not Equal to: a != b


if (condition) 
  // block of code to be executed if the condition is True
  //  block of code to be executed if the condition is False


int time = 20;
if (time < 10) 
  Console.WriteLine("Good morning.");
else if (time <= 20) 
  Console.WriteLine("Good day.");
  Console.WriteLine("Good evening.");
// Outputs "Good day."

11. C# Switch statement

Use the switch statement to select one of many code blocks to be executed.


  case x:
    // code block
  case y:
    // code block
    // code block


int day = 4;
switch (day) 
  case 1:
  case 2:
  case 3:
  case 4:
  case 5:
  case 6:
  case 7:
// Outputs "Thursday" (day 4)

12. C# Loops

C# supports for, while, do while loop and foreach loop.


for(int i = 0; i < 100; i++){
	// code block to be execute  

int i = 1;
while (i < 10) 
  	// code block to be executed
int j = 0;
  // code block to be executed
}while(j < 10)

var list = new[]{1,2,3,4,5,6,7,8,9,10};
foreach( var i in list){
	// Code block to be execute

13. C# break/continue

You have already seen the break statement used in an earlier chapter of this tutorial. It was used to “jump out” of a switch statement. The break statement can also be used to jump out of a loop. This example jumps out of the loop when i is equal to 4:

for (int i = 0; i < 10; i++) 
  if (i == 4) 

Example of “continue”:

for (int i = 0; i < 10; i++) 
  if (i == 4) 

14. C# Array

Arrays are used to store multiple values in a single variable, instead of declaring separate variables for each value. To declare an array, define the variable type with square brackets:

string[] cars;
string[] cars = {"Volvo", "BMW", "Ford", "Mazda"};

Access the Elements of an Array

string[] cars = {"Volvo", "BMW", "Ford", "Mazda"};

foreach( var c in cars){


C# is a very powerful and rich programming language. This article has given a brief idea about C# programming language. Thank you for your patience.

Next CSharp (C#) Object Oriented Programming

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