C# Cheatsheet Cheatsheet




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 typeDescriptionRangeMemory Size
byteused to store unsigned integer0 to 2551 byte
sbyteused to store signed integer-128 to 1271 byte
shortused to store signed integers-32,768 to 32,7672 bytes
intused to store signed integers-2,147,483,648 to 2,147,483,6474 bytes
longused to store signed integers-9,223,372,036,854,775,808 to 9,223,372,036,854,775,8078 bytes
floatused to store fractional numbers6 to 7 decimal digits4 bytes
doubleused to store fractional numbers15 decimal digits8 bytes
charused to store a single character enclosed in single quoteone character2 bytes
boolBoolean data typeStores either true or false1 bit
StringStores a sequence of characters enclosed in double quotesSequence of Characters2 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 nameDescription
str.Lengthto 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

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, ....... } ;


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