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title: C# date: 2021-12-14 12:22:00 background: bg-[#8c4c8a] tags: - object-oriented - class categories: - Programming intro: | C# quick reference cheat sheet that provides basic syntax and methods. plugins: - copyCode

Getting Started

Hello.cs

class Hello {
  // main method
  static void Main(string[] args)
  {
    // Output: Hello, world!
    Console.WriteLine("Hello, world!");
  }
}

Creates a project directory for new console application

$ dotnet new console

Lists all the applications templates

$ dotnet new list

Compiling and running (make sure you are in the project directory)

$ dotnet run
Hello, world!

Variables

int intNum = 9;
long longNum = 9999999;
float floatNum = 9.99F;
double doubleNum = 99.999;
decimal decimalNum = 99.9999M;
char letter = 'D';
bool @bool = true;
string site = "cheatsheets.zip";

var num = 999;
var str = "999";
var bo = false;

Primitive Data Types

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Comments

// Single-line comment

/* Multi-line
   comment */

// TODO: Adds comment to a task list in Visual Studio

/// Single-line comment used for documentation

/** Multi-line comment
    used for documentation **/

Strings

string first = "John";
string last = "Doe";

// string concatenation
string name = first + " " + last;
Console.WriteLine(name); // => John Doe

See: Strings

User Input

Console.WriteLine("Enter number:");
if(int.TryParse(Console.ReadLine(),out int input))
{
  // Input validated
  Console.WriteLine($"You entered {input}");
}

Conditionals

int j = 10;

if (j == 10) {
  Console.WriteLine("I get printed");
} else if (j > 10) {
  Console.WriteLine("I don't");
} else {
  Console.WriteLine("I also don't");
}

Arrays

char[] chars = new char[10];
chars[0] = 'a';
chars[1] = 'b';

string[] letters = {"A", "B", "C"};
int[] mylist = {100, 200};
bool[] answers = {true, false};

Loops

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

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

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

C# Strings

String concatenation

string first = "John";
string last = "Doe";

string name = first + " " + last;
Console.WriteLine(name); // => John Doe

String interpolation

string first = "John";
string last = "Doe";

string name = $"{first} {last}";
Console.WriteLine(name); // => John Doe

String Members {.row-span-2}

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Verbatim strings

string longString = @"I can type any characters in here !#@$%^&*()__+ '' \n \t except double quotes and I will be taken literally. I even work with multiple lines.";

Member Example

// Using property of System.String
string lengthOfString = "How long?";
lengthOfString.Length           // => 9

// Using methods of System.String
lengthOfString.Contains("How"); // => true

Misc

General .NET Terms {.col-span-2}

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