C# Cheat Sheet

A Programming › C cheat sheet in English by Ziggiboy

Just some stuff to help me remember

C-

8,492 views 1,477 downloads 15 May 2023 History

PRs

String methods

Length	Returns the number of characters in a string.
IndexOf	Finds the index of the first occurrence of a specified character or substring.
Substring	Retrieves a portion of the string based on a specified index or length.
ToUpper and ToLower	Converts a string to uppercase or lowercase, respectively
Trim	Removes leading and trailing whitespace characters from a string.
Replace	Replaces all occurrences of a specified character or substring with another.
Split	Splits a string into an array of substrings based on a specified delimiter.
Concat	Concatenates multiple strings into a single string.
Format	Formats a composite string by replacing placeholders with corresponding values.
Compare	Compares two strings and returns an integer indicating their relative order.
Contains	Determines whether a specified character or substring exists within a string.
StartsWith and EndsWith	Checks if a string starts or ends with a specified character or substring.
PadLeft and PadRight	Adds padding characters to the left or right of a string to achieve a specified length.
IsNullOrEmpty and IsNullOrWhiteSpace	Checks if a string is null, empty, or consists only of whitespace characters.
Join	oncatenates an array of strings into a single string, using a specified delimiter.
ToCharArray	Converts a string to an array of characters.
CompareTo	Compares two strings and returns an integer indicating their relative order.
Substring (overload with start index and length)	Retrieves a substring from a string, starting at a specified index and with a specified length.
Remove	Deletes a specified number of characters from a string, starting at a specified position.
Equals	Compares two strings for equality, taking into account culture-specific or case-sensitive comparisons.

Logical And Arithmetic Operators

&&	AND
\|\|	OR
+	Add
-	Subtract
*	Multiply
/	Divide
%	Modulo
++	Increase 1
--	Decrease 1

Arrays

**string[] planets =**
        **    {**
    **           "Mercury", "Venus", "Mars",**
        **       "Earth", "Jupiter", "Saturn", **
**               "Uranus", "Neptune", "Pluto"**
         **   };**

           ** for (int i = 0; i < planets.Length; i++)**
           ** {**
          **      Console.WriteLine(planets[i]);**
       **     }**

        **    foreach (string planet in planets)**
         **   {**
        **        Console.WriteLine(planet);**
        **    }**

-----------------------------------

**array sort & reverse:**
**string[] names = { "Jane", "Frank", "Alice", "Tom" };**

           ** Array.Sort(names);**
           ** foreach (string name in names)**
          **  {**
            **    Console.Write(name + " ");**
           ** }**

**Array.Reverse(names);**
           ** foreach (string name in names)**
           ** {**
             **   Console.Write(name + " ");**
        **    }**

Switch case

**switch(expression) {**
  ** case constant-expression1  :**
    **  statement(s);**
   **   break;**
  ** case constant-expression2  :**
   **case constant-expression3  :**
     ** statement(s);**
    **  break;**
  
  ** /* you can have any number of case statements */**
   **default : /* Optional */**
   **statement(s);**
**}**

While loop

while(condition)
{
statement(s);
}

Here, statement(s) may be a single statement or a block of statements. The condition may be any expression, and true is any non-zero value. The loop iterates while the condition is true.

When the condition becomes false, program control passes to the line immediately following the loop.

do while loop

do
{
statement(s);
} while( condition );

Notice that the conditional expression appears at the end of the loop, so the statement(s) in the loop execute once before the condition is tested.

If the condition is true, the flow of control jumps back up to do, and the statement(s) in the loop execute again. This process repeats until the given condition becomes false.

Classes and objects

**--Classes--**
**class Car **
**{**
**string color = "red";**
**}**

**--Object--**
**class Car **
**{**
**  string color = "red";**

**  static void Main(string[] args)**
**  {**
**    Car myObj = new Car();**
**    Console.WriteLine(myObj.color);**
**  }**
**}**

**--Multiple Objects--**
**class Car**
**{**
**  string color = "red";**
**  static void Main(string[] args)**
**  {**
**    Car myObj1 = new Car();**
**    Car myObj2 = new Car();**
**    Console.WriteLine(myObj1.color);**
**    Console.WriteLine(myObj2.color);**
**  }**
**}**

Comparison Operators

<	Less than
>	Greater than
<=	Less than or equal to
>=	Greater than or equal to
==	Equal to
!=	Not equal to

Comments

// Single line
/ Multiple

lines /
/// XML comments on single line

Assignment

=	Assignment
+=	Add
-=	Subtract

Lists

**List<int> number = new()**
           ** {**
               ** 4, 6, 8, 1, 10, 2, 7, 3, 9, 5**
           ** };**

           ** number.Add(12);**
           ** number.Add(11);**
           ** number.Remove(1);**
           ** number.Sort();**

            **foreach (int num in number)**
            **{**
               ** Console.WriteLine(num);**
          **  }**

**---------------------------------**
            
          **  List<string> word = new()**
          **  {**
             **   "Delta", "Charlie", "Bravo", "Foxtrot", **
           **     "Echo", "Alpha", "Golf"**
         **   };**

         **   word.Add("India");**
       **     word.Add("Hotel");**
          **  word.Remove("Alpha");**
           ** word.Sort();**

           ** foreach (string phonetic in word)**
          **  {**
           **     Console.WriteLine(phonetic);**
         **   }**

Casting

Implicit Casting (automatically)	converting a smaller type to a larger type size char -> int -> long -> float -> double.
Explicit Casting (manually)	converting a larger type to a smaller size type double -> float -> long -> int -> char.

Implicit Casting:
int myInt = 9;
double myDouble = myInt; // Automatic casting: int to double

Console.WriteLine(myInt); // Outputs 9
Console.WriteLine(myDouble); // Outputs 9

Explicit Casting:
double myDouble = 9.78;
int myInt = (int) myDouble; // Manual casting: double to int

Console.WriteLine(myDouble); // Outputs 9.78
Console.WriteLine(myInt); // Outputs 9

for loop

for ( init; condition; increment )
{
statement(s);
}

The init step is executed first, and only once. This step allows you to declare and initialize any loop control variables. You are not required to put a statement here, as long as a semicolon appears.

Next, the condition is evaluated. If it is true, the body of the loop is executed. If it is false, the body of the loop does not execute and flow of control jumps to the next statement just after the for loop.

After the body of the for loop executes, the flow of control jumps back up to the increment statement. This statement allows you to update any loop control variables. This statement can be left blank, as long as a semicolon appears after the condition.

The condition is now evaluated again. If it is true, the loop executes and the process repeats itself (body of loop, then increment step, and then again testing for a condition). After the condition becomes false, the for loop terminates.

Data types

bool	Represents a Boolean value, either true or false.
char	Represents a single Unicode character.
string	Represents a sequence of characters.
int	Represents signed integers (whole numbers) within the range -2,147,483,648 to 2,147,483,647.
double	Represents double-precision floating-point numbers with decimal values. Sufficient for storing 15 decimal digits
decimal	Represents decimal numbers with high precision and a larger range.
float	Represents single-precision floating-point numbers with decimal values. Sufficient for storing 6 to 7 decimal digits
long	Represents signed integers with a larger range than int, from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.
DateTime	Represents dates and times.

Example method

**namespace MyApplication**
**{**
**  class Program**
**  {**
**    static void Main(string[] args)**
**    {**
**      MyMethod();**
**    }**

**    static void MyMethod()**
**    {**
**      Console.WriteLine("I have a red banana");**
**    }**
**  }**
**}**

Ternary operator

condition ? consequent : alternative

string GetWeatherDisplay(double tempInCelsius) => tempInCelsius < 20.0 ? "Cold." : "Perfect!";

Console.WriteLine(GetWeatherDisplay(15)); // output: Cold.
Console.WriteLine(GetWeatherDisplay(27)); // output: Perfect!

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