C# Cheatsheet

1735

3 years ago

Basics

Sample Program

using System;

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

Using Keyword : using keyword is used to include namespaces in the program.
Namespace declaration : Namespace is a container for classes and other namespaces. The HelloWorld namespace contains the class Program.
Public Class : class is a container for data and methods, you are declaring Program as a class with public visibility.
Main : Beginning of your program
Console.WriteLine : Console is a class of the System namespace and WriteLine() is a method in it which is used to print text to the console.
C# statements end with a semicolon ;
C# is Case-sensitive
// : Single line Comment
/* */ : Multi Line Comments

Data types

Data type	Description	Range	Memory Size
byte	used to store unsigned integer	0 to 255	1 byte
sbyte	used to store signed integer	-128 to 127	1 byte
short	used to store signed integers	-32,768 to 32,767	2 bytes
int	used to store signed integers	-2,147,483,648 to 2,147,483,647	4 bytes
long	used to store signed integers	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807	8 bytes
float	used to store fractional numbers	6 to 7 decimal digits	4 bytes
double	used to store fractional numbers	15 decimal digits	8 bytes
char	used to store a single character enclosed in single quote	one character	2 bytes
bool	Boolean data type	Stores either true or false	1 bit
String	Stores a sequence of characters enclosed in double quotes	Sequence of Characters	2 bytes per character

Variables

datatype variableName = value;

int x = 10; // declaring int variable and assigning value 10 to it
char grade = 'A'; // declaring char variable and assigning value A to it

Constants

const datatype variable-name = value;

String functions

Function name	Description
str.Length	to return the length of string str
+	to concatenate two strings
string.Concat(str1,str2)	to concatenate two strings str1 and str2
Copy(str1, str2)	To copy string str2 into string str1.
Compare(str1, str2)	returns 0 if str1 and str2 are the same and less than 0 if str1 < str2 and a positive number if str1 > str2
Join(str, String[])	concatenate all the elements of the given string array with the specified separator between each element.
Split(Char[])	splits a string into substrings based on the characters in an array
str.ToUpper()	converts the string to upper case
str.ToLower()	converts the string to lower case
ToString()	to return instance of a string
Trim()	removes all leading and trailing whitespaces from a given string
Clone()	returns a reference to this instance of String
Format()	it returns a formatted string
LastIndexOf()	it returns the last occurence of the string
Replace()	it replaces the specified string character with new character
Contains()	it checks whether a string contains substring
ToCharArray()	it converts a string to a character(char) array
isEmpty()	it checks whether the string is empty or not and return true or false respectively
startsWith("char")	it checks the string start with given character or not and return true or false respectively
endsWith("char")	it checks the string end with given character or not and return true or false respectively
charAt(int)	it returns the character at the specified index in a string
## Conditional Statements

1. If

if(conditional-expression)
{
    //code
}

2. If-else

if(conditional-expression)
{
    //code
} else {
    //code
}

3. If-else-if ladder

if(conditional-expression-1)
{
    //code
} else if(conditional-expression-2) {
    //code
} else if(conditional-expression-3) {
    //code
}
....
else {
    //code
}

4. Switch

switch(conditional-expression){    
case value1:    
 //code    
 break;  //optional  
case value2:    
 //code    
 break;  //optional  
...    
    
default:     
 //code to be executed when all the above cases are not matched;    
}

Loops

1. For

for(Initialization; Condition; Increment/decrement){  
//code  
}

2. While

while(condition){  
//code 
}

3. Do-While

do{  
//code 
} while(condition);

Arrays

data-type[] array-name; //declaration
array-name = new data-type[size]{ array-elements }; //initialization

[or]

data-type[] array-name =  new data-type[size]{ array-elements }; //declaration and initialization

[or]

data-type[] array-name =  { array-elements }; //short syntax of array declaration and initialization

Examples

int[] num = {1,2,3,4,5};

Functions

<AccessSpecifier> <return-type> FunctionName(<parameters>)  // functin definition
{  
//code
}
function_name (parameters); // calling a function

Structures

struct structure_name {

   member definition;
   member definition;
   ...
   member definition;
}; 

structure_name variable name; //declaring structure variables

enum

enum name{constant1, constant2, constant3, ....... } ;