C# Quick Dev Reference

C# quick reference cheat sheet that provides basic syntax and methods.

Getting Started

Hello.cs

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

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 = "ref.softcrony.com";

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

Primitive Data Types

int — 4 bytes — -231 to 231-1

long — 8 bytes — -263 to 263-1

float — 4 bytes — 6 to 7 decimal digits

double — 8 bytes — 15 decimal digits

decimal — 16 bytes — 28 to 29 decimal digits

char — 2 bytes — 0 to 65535

bool — 1 bit — true / false

string — 2 bytes per char — N/A

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:

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]);
}

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

Length — A property that returns the length of the string.

Compare() — A static method that compares two strings.

Contains() — Determines if the string contains a specific substring.

Equals() — Determines if the two strings have the same character data.

Format() — Formats a string via the {0} notation and by using other primitives.

Trim() — Removes all instances of specific characters from trailing and leading characters. Defaults to removing leading and trailing spaces.

Split() — Removes the provided character and creates an array out of the remaining characters on either side.

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

Runtime — A collection of services that are required to execute a given compiled unit of code.

Common Language Runtime (CLR) — Primarily locates, loads, and managed .NET objects. The CLR also handles memory management, application hosting, coordination of threads, performaing security checks, and other low-level details.

Managed code — Code that compiles and runs on .NET runtime. C#/F#/VB are examples.

Unmanaged code — Code that compiles straight to machine code and cannot be directly hosted by the .NET runtime. Contains no free memory management, garbage collection, etc. DLLs created from C/C++ are examples.