/csharp-cheatsheet

Key terms & definitions

CSharp Cheat Sheet Template

Keyword Summary Sample Code Mentioned In
; Used to separate statements from each other int i = 5; i++; Console.WriteLine(i); Script Execution
// Used for single-line comments float multiplier = 0.01f; // % to float (e.g. 24% = 0.24) Comments
Variable Initialization When a value is assigned to a variable for the first time int a = 5; Variables
dotnet new console -o project-name For creating a new project using command prompt dotnet new console -o csharp-cheatsheet Console Basics Intro
Script Execution Order Be mindful of chronology e.g. Maths N/A N/A
Formatting ? ? ?
Console.WriteLine Write a comment in command. Use for testing & instructions. CW + TAB Printing Output
Console.Write Doesn't create new line. Can chain multiple together. Console.Write("Ouput"); Comments
Multi-Line Comment Turn more than one line of code into a comment /* Lines of text */ Comments
XML Documentation Comment Use three forward slashes for special comments /// <summary> /// details Comments
Variable Data storage units that consist of a name & a type. int x = 1; Console.WriteLine(x); Variables
Variable Declaration Always declare a variable before using one int x; int y; int z; Variables
Variable Assignment Use = sign to assign values to variables int z = (5+y) Variables
Uninitialized Variable A variable that's declared, but lacks a definite assigned value int k; k = k + 1; Variables
= (Assignment Operator) Assigns value to a variable, property, or indexer element. a = (b = c) Variables
Scope Three levels: Class, Method, & Block level public class ClassLevel { everythingElse } N/A
Variable Scope The reacha & validity of a variable {This.variableScope} Variables
int Integer: whole numbers postive: 1, negative : -1 Basic Data Types
float Fractional numbers + f (floating point numericals) 0.25f Basic Data Types
double Less accurate than float, but better performance & fractionals double a = 12.3; double bacteriaSize = 24e-10; Basic Data Types
bool True or false literal flags bool check = true; bool isWinning = false; Basic Data Types
char Uses unicode for single characters char euroSign = "€"; foreach(char c in helloWorld) {} Basic Data Types
string A full string string name = "Harry"; use "@" before quotations for multiline Basic Data Types
byte Assign variable within byte data range byte value1 = 64; byte someByte = 0xF1; Basic Data Types
Implicit Casting Give a direct value int i = 5; double d = 1; 5.0 d = 9.78; Conversion
Explicit Casting Converting fractional to whole comes with a loss of precision i = (int) d; // new value: 9 // string input = "2"; Conversion
Type Conversion Convert between types e.g. class to variable int num = 2147483647; long bigNum = num; Conversion
Convert.ToInt32 Convert to int e.g. from input i = Convert.ToInt32(input); Conversion
Operators Functions represented as symbols int add = 3 + 5; Operators
Arithmetic Operators Math operations public class Coin { public static Coins operator+ (Coin a, Coin b) {return new Coins (a, b);} Operators
+ add int add = 3 + 5; // 8 Operators
- sub int sub = 6 - 12; // -6 Operators
* multiply int mul = 3 * 4; // 12 Operators
/ divide int div = 9 / 3; // 3 Operators
% modulus int mod = 10 % 3; // = 1 Operators
+= assignment operator 1 a+=b -> a=a+b assignment operator 1
-= assignment operator 2 a−=b -> a=a−b assignment operator 1
++ incraments by 1 x++=11 Operators
-- decraments by 1 `double a = 1.5; cw (--a); // output: 0.5 assignment operator 1`
Post-Increment i++ increment the value then use it inside the expression int a, b = 15; a = b++; Operators
Pre-Increment ++i increment the value of a variable before using it in an expression int a, b = 15; a = ++b; Operators
System.Math A static class for solving math problems System.Math Math
static Something that can't be initiated or inherited static void Main() {} Math
Math.Max Finds the highest value int max = Math.Max(5, 3); // = 5 Math
Math.Min Find the lowest value int min = Math.Min(5, 3); // = 3 Math
Math.Sqrt Squareroot (what multiplied by itself equals this number) double sqrt = Math.Sqrt(16); // 4.0, because 4 * 4 = 16 Math
Math.Abs Absolute (always positive, good for distance) double abs = Math.Abs(-4.3); // 4.3 Math
Math.Round Uses statistical rounding to round to the nearest integer double round = Math.Round(12.6); // 13 Math
Math.Floor Rounds to the lower integer double floor = Math.Floor(12.6) // 12 Math
Math.Ceiling Rounds to the higher integer double ceil = Math.Ceiling(12.1); // 13 Math
Math.Clamp Clamps an int between two defined values double clamp = Math.Clamp(15, 0, 10); // 15 is clamped to 10 Math
Math.Pow Returns the value to the power of power double pow = Math.Pow(2, 3); // 8 (2^3 = 2 * 2 * 2 = 8) Math
string.Length Returns the numerical length of a string string length = firstName.Length; Strings
string.ToUpper Turns a string into ALL-CAPS. ToLower does the opposite. string upper = firstName.ToUpper(); // JOHN Strings
string.+ String strings together string fullName = firstName + " " + lastName; // John Kane Strings
$"{}" String strings and variables together using interpolation string interp = $"{firstName} {lastName}"; // John Kane Strings
string.[] Get a certain letter or character from a string e.g. initials char char1 = firstName[0]; // 'J' Strings
string.IndexOf Get an index of a first occurence of a character or string int index = firstName.IndexOf("h"); // 2 Strings
string.SubString(int) Get a subpart of a string starting at an inputted value string sub = firstName.SubString(1); // "ohn" Strings string.Substring(int, int)
string.Replace Replace all occurences of a character with another string replace = fullName.Replace( 'n', 'd'); // "Johd Kade" Strings
immutable Something that can never be changed string fullName = "John Kane"; fullName = fullName.Replace('n', 'd'); cw(fullName); // Johd Kade Strings
Logical Operators Logical constants used to connect two or more formulas Three types: and , or , and not Logical Operators
! Inverse a logical operator !false -> true Logical Operators
&& Combine two bool values [AND] bool x = true; bool y = true; bool z = x && y = true; // true Logical Operators
Comparison Operators Compare two values to return a bool Equal to, greater than, less than etc. Comparison Operators
> Greater than bool isGreater = 10 > 9; // True Comparison Operators
== Is equal to bool isEqual = 10 == 9; // False Comparison Operators
!= IS NOT equal to bool isNotEqual = 10 != 9; // True Comparison Operators
|| Check if one of several values is true or false bool x = true; bool y = false; bool z = x && y = true; // true Logical Operators
>= Greater OR equal to bool isGreaterOrEqual = 10>= 9; // True Comparison Operators
<= ? bool isLowerOrEqual = 10<= 9; // False ?
if Code that only executes if it's condition is met int hour = GetHour(); if (hour <12) { cw("Good morning!"); } If .. Else
else if Alternate condition that could be met Else if (hour <18) { cw("Good Day!"); } If .. Else
else If no other condition is met else { cw ("Good Evening!"); } If .. Else
? : Ternary if-operator. A shortcut for: if something equals X do this, otherwise do that string greeting = hour < 12 ? "Good Morning!" : "Good Day!"; If .. Else
Flow Control Statements Order in which statements or instructions are executed N/A If .. Else
System.Random Creates Random values Random random = new Random(); Random
pseudo-random ? ? ?
seed ? ? ?
Random.Next(int, int) ? ? ?
Random.Next() ? ? ?
Random.NextDouble() ? ? ?
Random.Next() ? ? ?
while ? ? ?
bool-expression ? ? ?
do..while ? ? ?
for ? ? ?
iteration statement ? ? ?
loop body ? ? ?
loop ? ? ?
execution ? ? ?
execution jump ? ? ?
break ? ? ?
continue ? ? ?
Array ? ? ?
int[] ? ? ?
Array Initialization ? ? ?
Array Access for Assignment ? ? ?
Array Access for Reading ? ? ?
Array.Resize ? ? ?
Array.Length ? ? ?
foreach ? ? ?
2D-Array ? ? ?
2D-Array Initialization ? ? ?
2D-Array Access for Assignment ? ? ?
2D-Array Access for Reading ? ? ?
Jagged Arrays ? ? ?
Method ? ? ?
void ? ? ?
Return Type ? ? ?
() ? ? ?
Parameter ? ? ?
Argument ? ? ?
Parameter ? ? ?
Parameter-List ? ? ?
Named Arguments ? ? ?
Optional Arguments ? ? ?
Default Value ? ? ?
return ? ? ?
Code Paths ? ? ?
Method Overloading ? ? ?
Object-Oriented Programming ? ? ?
Data ? ? ?
Function ? ? ?
Structured Programming ? ? ?
Objects ? ? ?
Instance Method ? ? ?
Class ? ? ?
Type ? ? ?
class ? ? ?
new ? ? ?
Class Member ? ? ?
Class Instance ? ? ?
Garbage Collector ? ? ?
null ? ? ?
Invoke ? ? ?
Field ? ? ?
Static Class Member ? ? ?
Static Class ? ? ?
Global Access ? ? ?
Constructor ? ? ?
Initial Class Values ? ? ?
Parameterless ? ? ?
Default Contructor ? ? ?
Finalizer ? ? ?
Object Destruction ? ? ?
GC.Collect ? ? ?
Encapsulation ? ? ?
Access Modifier ? ? ?
private ? ? ?
protected ? ? ?
public ? ? ?
internal ? ? ?
Class Member Access ? ? ?
Inheritance ? ? ?
Property ? ? ?
Getter Method ? ? ?
Setter Method ? ? ?
Validation ? ? ?
Processing ? ? ?
get ? ? ?
set ? ? ?
Expression Body Syntax ? ? ?
Auto Property ? ? ?
Read-Only Property ? ? ?
Auto Property ? ? ?
base-Class ? ? ?
Inherit From ? ? ?
Derived Class ? ? ?
Child Class ? ? ?
Parent Class ? ? ?
sealed ? ? ?
Polymorphism ? ? ?
as ? ? ?
virtual ? ? ?
override ? ? ?
base ? ? ?
Abstraction ? ? ?
abstract ? ? ?
Implementation ? ? ?
Composition ? ? ?
"Composition over Inheritance" ? ? ?