C#

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Introduction

C# (pronounced C-sharp) is part of the Microsoft .Net architecture. Many people argue that C# is more of a competitor to Java (and specifically to Sun Microsystems) than to C or C++. Officially Microsoft states that it is an evolution of C/C++.

Essentially C# is a purely object oriented development environment that incorporates a garbage collection mechanism to clear memory of no longer used data.

C# is an object-oriented language supporting:

	Namespaces - allow developers to group related types into hierarchical categories.
	Inheritance - from one class to others (multiple inheritance to a class is not allowed); new classes can be customized.
	Polymorphism - the ability to perform the same operation across a number of types (as long as they share common characteristics).

C# applications programming depends upon the .Net Framework which provides a robust set of services and libraries. This includes both the framework class library (FCL) and the Common Language Runtime (CLS).

The Framework Class Library (FCL) includes the following libraries:

	Object Class - root of the class hierarchy and serves as base class for all others.
	Math - including special data types (decimal for money), math functions (trig, etc.), and random number generation.
	String - formatting, indexing, and encoding
	Collections - data arrays to supplement standard arrays.
	Regular Expressions - expression matching and replacement.
	Input/Output
	Networking

Language Fundamentals

Program Structure and Organization

A C# program is built by building new types and using existing ones created in C# language or imported from other libraries.

C# programs can consist of one or more files.

	Each file can contain one or more namespaces.
	A namespace can contain types such as classes, structs, interfaces, enumerations, and delegates, in addition to other namespaces.

The following is the skeleton of a C# program that contains all of these elements.

// A skeleton of a C# program
using System;
namespace MyNamespace1
{
   class MyClass1
   {
   }
   struct MyStruct
   {
   }
   interface IMyInterface
   {
   }
   delegate int MyDelegate();
   enum MyEnum
   {
   }
   namespace MyNamespace2
   {
   }
   class MyClass2
   {
      public static void Main(string[] args)
      {
      }
   }
}

--from Microsoft C# Reference site

Commenting code:

// comment

/* multiline
comment */

Program delivery: compiled

	Primarily via tools by Microsoft
	http://www.c-point.com/csharp.htm also has a C# development product.

Key words in C#

abstract	event	new	struct
as	explicit	null	switch
base	extern	object	this
bool	false	operator	throw
break	finally	out	true
byte	fixed	override	try
case	float	params	typeof
catch	for	private	uint
char	foreach	protected	ulong
checked	goto	public	unchecked
class	if	readonly	unsafe
const	implicit	ref	ushort
continue	in	return	using
decimal	int	sbyte	virtual
default	interface	sealed	volatile
delegate	internal	short	void
do	is	sizeof	while
double	lock	stackalloc
else	long	static
enum	namespace	string

Data Types

Storage size
Decimal	decimal
Date	DataTime (.NET Framework class)
(varies)	String
1 byte	Byte
2 bytes	Boolean - bool
2 bytes	short, char (Unicode character)
4 bytes	int
8 bytes	long
4 bytes	float
8 bytes	double

Arrays - C# supports arrays (zero referent). It also support multi-dimensional arrays as both rectangular (n-dimensional blocks) and jagged (arrays of arrays).

Variables

The C# typing system contains the following categories:

Value types -- the value types consist of two main categories:

Struct type (integral, floating point, decimal, bool)
Enumeration type: used to declare an enumeration, a distinct type consisting of a set of named constants called the enumerator list

Reference types - also referred to as objects, store references to the actual data; 3 keywords are used to declare reference types:

	class
	interface -- defines a contract. A class or struct that implements an interface must adhere to its contract.
	delegate -- defines a reference type that can be used to encapsulate a method with a specific signature. A delegate instance encapsulates a static or an instance method. Delegates are roughly similar to function pointers in C++; however, delegates are type-safe and secure.

Pointer types

Variables of the value types store data, while those of the reference types store references to the actual data. Reference types are also referred to as objects. Pointer types can be used only in unsafe mode.

It is possible to convert a value type to a reference type and vice versa, by using boxing and unboxing.

Expressions and Operators

Addition	+
Subtraction	-
Multiplication	*
Division	/
Integer division	/¹
Modulus (division returning only the remainder)	%
Exponentiation	n/a
Assignment
Assignment	=
Addition	+=
Subtraction	-=
Multiplication	*=
Division	/=
Integer division	/=¹
Concatenate	+=
Modulus	%=
Left shift	<<=
Right shift	>>=
Bitwise-AND	&=
Bitwise-exclusive-OR	^=
Bitwise-inclusive-OR	\|=
Relational/equality
Less than	<
Less than or equal to	<=
Greater than	>
Greater than or equal to	>=
Equal	==
Not equal	!=
Compare two object reference variables	==
Compare object reference type	x is Class1 (also see as and typeof)
Compare strings	== -or-String.Equals()
Concatenate strings	+
Shortcircuited Boolean AND	&&
Shortcircuited Boolean OR	\|\|
Shift
Left shift	<<
Right shift	>>
Scope resolution
Scope resolution	. and base
Postfix(highest order of resolution)
Array element	[ ]
Function call	( )
Type cast	(type)
Member selection	.
Postfix increment	++
Postfix decrement	--
Unary
Indirection	* (unsafe mode only)
Address of	& (unsafe mode only; also see fixed)
Logical-NOT	!
One's complement	~
Prefix increment	++
Prefix decrement	--
Size of type	sizeof
comma	n/a
Bitwise
Bitwise-AND	&
Bitwise-exclusive-OR	^
Bitwise-inclusive-OR	\|
Logical
Logical-AND	&&
Logical-OR	\|\|
Conditional
Conditional	?:
Pointer to member
Pointer to member	. (Unsafe mode only)
Reference
Reference	n/a (use reference types)

Control Statements

If-then

The if statement selects a statement for execution based on the value of a Boolean expression. It takes the following form:
if (expression)
   statement1
[else
   statement2]
where:

expression

An expression that can be implicitly converted to bool or a type that contains overloading of the true and false operators.

statement1

The embedded statement(s) to be executed if expression is true.

statement2

The embedded statement(s) to be executed if expression is false.

Switch

The switch statement is a control statement that handles multiple selections by passing control to one of the case statements within its body. It takes the following form:
switch (expression)
{
   case constant-expression:
      statement
      jump-statement
   [default:
      statement
      jump-statement]
}
Where:

expression

An integral or string type expression.

statement

The embedded statement(s) to be executed if control is transferred to the case or the default.

jump-statement

A jump statement that transfers control out of the case body.

constant-expression

Control is transferred to a specific case according to the value of this expression.

Do loop

The do statement executes a statement or a block of statements repeatedly until a specified expression evaluates to false. It takes the following form:
do statement while (expression);
where:

expression

An expression that can be implicitly converted to bool or a type that contains overloading of the true and false operators. The expression is used to test the loop-termination criteria.

statement

The embedded statement(s) to be executed.

For loop

The for loop executes a statement or a block of statements repeatedly until a specified expression evaluates to false. It takes the following form:
for ([initializers]; [expression]; [iterators]) statement
where:

initializers

A comma separated list of expressions or assignment statements to initialize the loop counters.

expression

An expression that can be implicitly converted to bool or a type that contains overloading of the true and false operators. The expression is used to test the loop-termination criteria.

iterators

Expression statement(s) to increment or decrement the loop counters.

statement

The embedded statement(s) to executed.

The foreach statement repeats a group of embedded statements for each element in an array or an object collection. The foreach statement is used to iterate through the collection to get the desired information, but should not be used to change the contents of the collection to avoid unpredictable side effects. The statement takes the following form:

While

The while statement executes a statement or a block of statements until a specified expression evaluates to false. It takes the following form:
while (expression) statement
where:

expression

An expression that can be implicitly converted to bool or a type that contains overloading of the true and false operators. The expression is used to test the loop-termination criteria.

statement

The embedded statement(s) to be executed.

Jump statements in C#:

	Break - exit from a loop.
	Continue - skips remaining steps, starts on next iteration of a loop.
	GoTo - transfers control to a label.
	Return - exits a method.
	Throw - "throws" an exception to indicate that an abnormal condition has occurred.
	Lock - calls 'enter' and 'exit' methods for the monitor class.
	Using - enables declaring, using, and disposing of disposable objects (e.g., file handling).

Input/Output

	Command Line: via the console object interfaces.
	GUI: via the Visual Studio .Net development environments. This includes use of windows and standard GUI objects (text boxes, buttons, etc.).
	File I/O: via low-level and system level objects.
	Database: via ADO, ADO.Net and similar database integration technologies.

Resources

References

	Google Directory: http://directory.google.com/Top/Computers/Programming/Languages/C-sharp/
	Microsoft MSDN Reference
	Developersdex C# references

Tutorials

C# Station

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