learnxinyminutes-docs/csharp.html.markdown

---

language: c#
contributors:
    - ["Irfan Charania", "https://github.com/irfancharania"]
filename: LearnCSharp.cs

---

C# is an elegant and type-safe object-oriented language that enables developers to build a variety of secure and robust applications that run on the .NET Framework.

[Read more here.](http://msdn.microsoft.com/en-us/library/vstudio/z1zx9t92.aspx)

```c#
// Single-line comments start with //
/*
Multi-line comments look like this
*/
/// <summary>
/// This is an XML documentation comment
/// </summary>


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

// defines scope to organize code into "packages"
namespace Learning
{
	// Each .cs file should at least contain a class with the same name as the file
	// you're allowed to do otherwise, but shouldn't for sanity.
	public class LearnCSharp
	{
		// A console application must have a main method as an entry point
		public static void Main(string[] args)
		{
			// Use Console.WriteLine to print lines
			Console.WriteLine("Hello World");
			Console.WriteLine(
				"Integer: " + 10 +
				" Double: " + 3.14 +
				" Boolean: " + true);

			// To print without a new line, use Console.Write
			Console.Write("Hello ");
			Console.Write("World");


			///////////////////////////////////////////////////
			// Types & Variables
			//
			// Declare a variable using <type> <name>
			///////////////////////////////////////////////////

			// Sbyte - Signed 8-bit integer
			// (-128 <= sbyte <= 127)
			sbyte fooSbyte = 100;

			// Byte - Unsigned 8-bit integer
			// (0 <= byte <= 255)
			byte fooByte = 100;

			// Short - Signed 16-bit integer
			// (-32,768 <= short <= 32,767)
			short fooShort = 10000;

			// Ushort - Unsigned 16-bit integer
			// (0 <= ushort <= 65,535)
			ushort fooUshort = 10000;

			// Integer - Signed 32-bit integer
			// (-2,147,483,648 <= int <= 2,147,483,647)
			int fooInt = 1;

			// Uinteger - Unsigned 32-bit integer
			// (0 <= uint <= 4,294,967,295)
			uint fooUint = 1;

			// Long - Signed 64-bit integer
			// (-9,223,372,036,854,775,808 <= long <= 9,223,372,036,854,775,807)
			long fooLong = 100000L;
			// L is used to denote that this variable value is of type long or ulong
			// anything without is treated as int or uint depending on size.

			// Ulong - Unsigned 64-bit integer
			// (0 <= ulong <= 18,446,744,073,709,551,615)
			ulong fooUlong = 100000L;

			// Float - Single-precision 32-bit IEEE 754 Floating Point
			// Precision: 7 digits
			float fooFloat = 234.5f;
			// f is used to denote that this variable value is of type float;
			// otherwise it is treated as double.

			// Double - Double-precision 64-bit IEEE 754 Floating Point
			// Precision: 15-16 digits
			double fooDouble = 123.4;

			// Bool - true & false
			bool fooBoolean = true;
			bool barBoolean = false;

			// Char - A single 16-bit Unicode character
			char fooChar = 'A';

			// Strings
			string fooString = "My string is here!";
			Console.WriteLine(fooString);

			// formatting
			string fooFormattedString = string.Format("Check Check, {0} {1}, {0} {1:0.0}", 1, 2);
			Console.WriteLine(fooFormattedString);

			// formatting dates
			DateTime fooDate = DateTime.Now;
			Console.WriteLine(fooDate.ToString("hh:mm, dd MMM yyyy"));

			// \n is an escaped character that starts a new line
			string barString = "Printing on a new line?\nNo Problem!";
			Console.WriteLine(barString);

			// it can be written prettier by using the @ symbol
			string bazString = @"Here's some stuff
	on a new line!";
			Console.WriteLine(bazString);

			// quotes need to be escaped
			// use \" normally
			string quotedString = "some \"quoted\" stuff";
			Console.WriteLine(quotedString);

			// use "" when strings start with @
			string quotedString2 = @"some MORE ""quoted"" stuff";
			Console.WriteLine(quotedString2);

			// Use const or read-only to make a variable immutable
			// const values are calculated at compile time
			const int HOURS_I_WORK_PER_WEEK = 9001;

			// Nullable types
			// any type can be made nullable by suffixing a ?
			// <type>? <var name> = <value>
			int? nullable = null;
			Console.WriteLine("Nullable variable: " + nullable);

			// ?? is syntactic sugar for specifying default value
			// in case variable is null
			int notNullable = nullable ?? 0;
			Console.WriteLine("Not nullable variable: " + notNullable);

			// Var - compiler will choose the most appropriate type based on value
			var fooImplicit = true;

			///////////////////////////////////////////////////
			// Data Structures
			///////////////////////////////////////////////////
			Console.WriteLine("\n->Data Structures");

			// Arrays
			// The array size must be decided upon declaration
			// The format for declaring an array is follows:
			// <datatype>[] <var name> = new <datatype>[<array size>];
			int[] intArray = new int[10];
			string[] stringArray = new string[1];
			bool[] boolArray = new bool[100];

			// Another way to declare & initialize an array
			int[] y = { 9000, 1000, 1337 };

			// Indexing an array - Accessing an element
			Console.WriteLine("intArray @ 0: " + intArray[0]);

			// Arrays are zero-indexed and mutable.
			intArray[1] = 1;
			Console.WriteLine("intArray @ 1: " + intArray[1]); // => 1

			// Lists
			// Lists are used more frequently than arrays as they are more flexible
			// The format for declaring a list is follows:
			// List<datatype> <var name> = new List<datatype>();
			List<int> intList = new List<int>();
			List<string> stringList = new List<string>();

			// Another way to declare & initialize a list
			List<int> z = new List<int> { 9000, 1000, 1337 };

			// Indexing a list - Accessing an element
			// Lists are zero-indexed and mutable.
			Console.WriteLine("z @ 0: " + z[2]);

			// Lists don't default to a value;
			// A value must be added before accessing the index
			intList.Add(1);
			Console.WriteLine("intList @ 0: " + intList[0]);


			// Others data structures to check out:
			//
			// Stack/Queue
			// Dictionary
			// Read-only Collections
			// Tuple (.Net 4+)


			///////////////////////////////////////
			// Operators
			///////////////////////////////////////
			Console.WriteLine("\n->Operators");

			int i1 = 1, i2 = 2; // Shorthand for multiple declarations

			// Arithmetic is straightforward
			Console.WriteLine("1+2 = " + (i1 + i2)); // => 3
			Console.WriteLine("2-1 = " + (i2 - i1)); // => 1
			Console.WriteLine("2*1 = " + (i2 * i1)); // => 2
			Console.WriteLine("1/2 = " + (i1 / i2)); // => 0 (0.5 truncated down)

			// Modulo
			Console.WriteLine("11%3 = " + (11 % 3)); // => 2

			// Comparison operators
			Console.WriteLine("3 == 2? " + (3 == 2)); // => false
			Console.WriteLine("3 != 2? " + (3 != 2)); // => true
			Console.WriteLine("3 > 2? " + (3 > 2)); // => true
			Console.WriteLine("3 < 2? " + (3 < 2)); // => false
			Console.WriteLine("2 <= 2? " + (2 <= 2)); // => true
			Console.WriteLine("2 >= 2? " + (2 >= 2)); // => true

			// Bitwise operators!
			/*
			~       Unary bitwise complement
			<<      Signed left shift
			>>      Signed right shift
			>>>     Unsigned right shift
			&       Bitwise AND
			^       Bitwise exclusive OR
			|       Bitwise inclusive OR
			*/

			// Incrementations
			int i = 0;
			Console.WriteLine("\n->Inc/Dec-rementation");
			Console.WriteLine(i++); //i = 1. Post-Incrementation
			Console.WriteLine(++i); //i = 2. Pre-Incrementation
			Console.WriteLine(i--); //i = 1. Post-Decrementation
			Console.WriteLine(--i); //i = 0. Pre-Decrementation


			///////////////////////////////////////
			// Control Structures
			///////////////////////////////////////
			Console.WriteLine("\n->Control Structures");

			// If statements are c-like
			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");
			}

			// Ternary operators
			// A simple if/else can be written as follows
			// <condition> ? <true> : <false>
			string isTrue = (true) ? "True" : "False";
			Console.WriteLine("Ternary demo: " + isTrue);


			// While loop
			int fooWhile = 0;
			while (fooWhile < 100)
			{
				//Console.WriteLine(fooWhile);
				//Increment the counter
				//Iterated 99 times, fooWhile 0->99
				fooWhile++;
			}
			Console.WriteLine("fooWhile Value: " + fooWhile);

			// Do While Loop
			int fooDoWhile = 0;
			do
			{
				//Console.WriteLine(fooDoWhile);
				//Increment the counter
				//Iterated 99 times, fooDoWhile 0->99
				fooDoWhile++;
			} while (fooDoWhile < 100);
			Console.WriteLine("fooDoWhile Value: " + fooDoWhile);

			// For Loop
			int fooFor;
			//for loop structure => for(<start_statement>; <conditional>; <step>)
			for (fooFor = 0; fooFor < 10; fooFor++)
			{
				//Console.WriteLine(fooFor);
				//Iterated 10 times, fooFor 0->9
			}
			Console.WriteLine("fooFor Value: " + fooFor);

			// Switch Case
			// A switch works with the byte, short, char, and int data types.
			// It also works with enumerated types (discussed in Enum Types),
			// the String class, and a few special classes that wrap
			// primitive types: Character, Byte, Short, and Integer.
			int month = 3;
			string monthString;
			switch (month)
			{
				case 1:
					monthString = "January";
					break;
				case 2:
					monthString = "February";
					break;
				case 3:
					monthString = "March";
					break;
				default:
					monthString = "Some other month";
					break;
			}
			Console.WriteLine("Switch Case Result: " + monthString);


			///////////////////////////////////////
			// Converting Data Types And Typcasting
			///////////////////////////////////////

			// Converting data

			// Convert String To Integer
			// this will throw an Exception on failure
			int.Parse("123");//returns an integer version of "123"

			// try parse will default to type default on failure
			// in this case: 0
			int tryInt;
			int.TryParse("123", out tryInt);

			// Convert Integer To String
			// Convert class has a number of methods to facilitate conversions
			Convert.ToString(123);

			///////////////////////////////////////
			// Classes And Functions
			///////////////////////////////////////

			Console.WriteLine("\n->Classes & Functions");

			// (definition of the Bicycle class follows)

			// Use new to instantiate a class
			Bicycle trek = new Bicycle();

			// Call object methods
			trek.speedUp(3); // You should always use setter and getter methods
			trek.setCadence(100);

			// ToString is a convention to display the value of this Object.
			Console.WriteLine("trek info: " + trek.ToString());

			// Instantiate another new Bicycle
			Bicycle octo = new Bicycle(5, 10);
			Console.WriteLine("octo info: " + octo.ToString());

			// Instantiate a new Penny Farthing
			PennyFarthing funbike = new PennyFarthing(1, 10);
			Console.WriteLine("funbike info: " + funbike.ToString());

			Console.Read();
		} // End main method


	} // End LearnCSharp class

	// You can include other classes in a .cs file


	// Class Declaration Syntax:
	// <public/private/protected> class <class name>{
	//    //data fields, constructors, functions all inside.
	//    //functions are called as methods in Java.
	// }

	public class Bicycle
	{
		// Bicycle's Fields/Variables
		public int cadence; // Public: Can be accessed from anywhere
		private int _speed;  // Private: Only accessible from within the class
		protected int gear; // Protected: Accessible from the class and subclasses
		internal int wheels; // Internal: Accessible from within the assembly
		string name; // default: Only accessible from within this class

		// readonly values are set at run time
		// they can only be assigned upon declaration or in a constructor
		readonly bool hasCardsInSpokes = false; // read-only private

		// Constructors are a way of creating classes
		// This is a default constructor
		public Bicycle()
		{
			gear = 1;
			cadence = 50;
			_speed = 5;
			name = "Bontrager";
		}

		// This is a specified constructor (it contains arguments)
		public Bicycle(int startCadence, int startSpeed, int startGear, string name, bool hasCardsInSpokes)
		{
			this.gear = startGear;
			this.cadence = startCadence;
			this._speed = startSpeed;
			this.name = name;
			this.hasCardsInSpokes = hasCardsInSpokes;
		}

		// Constructors can be chained
		public Bicycle(int startCadence, int startSpeed) :
			this(startCadence, startSpeed, 0, "big wheels", true)
		{
		}

		// Function Syntax:
		// <public/private/protected> <return type> <function name>(<args>)

		// classes can implement getters and setters for their fields
		// or they can implement properties

		// Method declaration syntax:
		// <scope> <return type> <method name>(<args>)
		public int getCadence()
		{
			return cadence;
		}

		// void methods require no return statement
		public void setCadence(int newValue)
		{
			cadence = newValue;
		}

		// virtual keyword indicates this method can be overridden
		public virtual void setGear(int newValue)
		{
			gear = newValue;
		}

		public void speedUp(int increment)
		{
			_speed += increment;
		}

		public void slowDown(int decrement)
		{
			_speed -= decrement;
		}

		// properties get/set values
		// when only data needs to be accessed, consider using properties.
		// properties may have either get or set, or both
		private bool _hasTassles; // private variable
		public bool hasTassles // public accessor
		{
			get { return _hasTassles; }
			set { _hasTassles = value; }
		}

		private int _frameSize;
		public int FrameSize
		{
			get { return _frameSize; }
			// you are able to specify access modifiers for either get or set
			// this means only Bicycle class can call set on Framesize
			private set { _frameSize = value; }
		}

		//Method to display the attribute values of this Object.
		public override string ToString()
		{
			return "gear: " + gear +
					" cadence: " + cadence +
					" speed: " + _speed +
					" name: " + name +
					" cards in spokes: " + (hasCardsInSpokes ? "yes" : "no") +
					"\n------------------------------\n"
					;
		}
	} // end class Bicycle

	// PennyFarthing is a subclass of Bicycle
	class PennyFarthing : Bicycle
	{
		// (Penny Farthings are those bicycles with the big front wheel.
		// They have no gears.)

		// calling parent constructor
		public PennyFarthing(int startCadence, int startSpeed) :
			base(startCadence, startSpeed, 0, "PennyFarthing", true)
		{
		}

		public override void setGear(int gear)
		{
			gear = 0;
		}
	}
} // End Namespace

```

## Topics Not Covered

 * Enums, Flags
 * Attributes
 * Generics (T), Delegates, Func, Actions, lambda expressions
 * Exceptions, Interfaces, Abstraction
 * LINQ
 * ASP.NET (Web Forms/MVC/WebMatrix)
 * Winforms
 * Windows Presentation Foundation (WPF)



## Further Reading

 * [DotNetPerls](http://www.dotnetperls.com)
 * [C# in Depth](http://manning.com/skeet2)
 * [Programming C#](http://shop.oreilly.com/product/0636920024064.do)
 * [LINQ](http://shop.oreilly.com/product/9780596519254.do)
 * [MSDN Library](http://msdn.microsoft.com/en-us/library/618ayhy6.aspx)
 * [ASP.NET MVC Tutorials](http://www.asp.net/mvc/tutorials)
 * [ASP.NET Web Matrix Tutorials](http://www.asp.net/web-pages/tutorials)
 * [ASP.NET Web Forms Tutorials](http://www.asp.net/web-forms/tutorials)
 * [Windows Forms Programming in C#](http://www.amazon.com/Windows-Forms-Programming-Chris-Sells/dp/0321116208)



[C# Coding Conventions](http://msdn.microsoft.com/en-us/library/vstudio/ff926074.aspx)