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Introduction to C#Introduction to C#

Anders Hejlsberg Anders Hejlsberg

Distinguished Engineer Distinguished Engineer

Developer Division Developer Division

Microsoft Corporation Microsoft Corporation

C# – The Big IdeasC# – The Big Ideas

 The first component orientedThe first component oriented

language in the C/C++ familylanguage in the C/C++ family

 Everything really is an objectEverything really is an object

 Next generation robust andNext generation robust and

durable softwaredurable software

 Preservation of investmentPreservation of investment

C# – The Big IdeasC# – The Big Ideas

Everything really is an object Everything really is an object

 Traditional viewsTraditional views

 C++, Java: Primitive types are “magic” and doC++, Java: Primitive types are “magic” and do

not interoperate with objectsnot interoperate with objects

 Smalltalk, Lisp: Primitive types are objects, butSmalltalk, Lisp: Primitive types are objects, but

at great performance costat great performance cost

 C# unifies with no performance costC# unifies with no performance cost

 Deep simplicity throughout systemDeep simplicity throughout system

 Improved extensibility and reusabilityImproved extensibility and reusability

 New primitive types: Decimal, SQL…New primitive types: Decimal, SQL…

 Collections, etc., work for allCollections, etc., work for all typestypes

C# – The Big IdeasC# – The Big Ideas

Robust and durable software Robust and durable software

 Garbage collectionGarbage collection

 No memory leaks and stray pointersNo memory leaks and stray pointers

 ExceptionsExceptions

 Error handling is not an afterthoughtError handling is not an afterthought

 Type-safetyType-safety

 No uninitialized variables, unsafe castsNo uninitialized variables, unsafe casts

 VersioningVersioning

 Pervasive versioning considerations inPervasive versioning considerations in

all aspects of language designall aspects of language design

Hello WorldHello World

using System; using System;

class Hello class Hello

static void Main() { static void Main() {

Console.WriteLine("Hello world"); Console.WriteLine("Hello world");

C# Program StructureC# Program Structure

 NamespacesNamespaces

 Contain types and other namespacesContain types and other namespaces

 Type declarationsType declarations

 Classes, structs, interfaces, enums,Classes, structs, interfaces, enums,

and delegatesand delegates

 MembersMembers

 Constants, fields, methods, properties, indexers,Constants, fields, methods, properties, indexers,

events, operators, constructors, destructorsevents, operators, constructors, destructors

 OrganizationOrganization

 No header files, code written “in-line”No header files, code written “in-line”

 No declaration order dependenceNo declaration order dependence

Type SystemType System

 Value typesValue types

 Directly contain dataDirectly contain data

 Cannot be nullCannot be null

 Reference typesReference types

 Contain references to objectsContain references to objects

 May be nullMay be null

int int ii == 123;123; stringstring ss == "Hello"Hello world";world";

ii (^123123)

s s (^) "Hello"Hello world"world"

Type SystemType System

 Value typesValue types

 PrimitivesPrimitives int i;int i;

 EnumsEnums enum State { Off, On }enum State { Off, On }

 StructsStructs struct Point { int x, y; }struct Point { int x, y; }

 Reference typesReference types

 ClassesClasses class Foo: Bar, IFoo {...}class Foo: Bar, IFoo {...}

 InterfacesInterfaces interface IFoo: IBar {...}interface IFoo: IBar {...}

 ArraysArrays string[]string[] aa == newnew string[10];string[10];

 DelegatesDelegates delegate void Empty();delegate void Empty();

ClassesClasses

 Single inheritanceSingle inheritance

 Multiple interface implementationMultiple interface implementation

 Class membersClass members

 Constants, fields, methods, properties,Constants, fields, methods, properties,

indexers, events, operators,indexers, events, operators,

constructors, destructorsconstructors, destructors

 Static and instance membersStatic and instance members

 Nested typesNested types

 Member accessMember access

 public, protected, internal, privatepublic, protected, internal, private

StructsStructs

 Like classes, exceptLike classes, except

 Stored in-line, not heap allocatedStored in-line, not heap allocated

 Assignment copies data, not referenceAssignment copies data, not reference

 No inheritanceNo inheritance

 Ideal for light weight objectsIdeal for light weight objects

 Complex, point, rectangle, colorComplex, point, rectangle, color

 int, float, double, etc., are all structsint, float, double, etc., are all structs

 BenefitsBenefits

 No heap allocation, less GC pressureNo heap allocation, less GC pressure

 More efficient use of memoryMore efficient use of memory

InterfacesInterfaces

 Multiple inheritanceMultiple inheritance

 Can contain methods, properties,Can contain methods, properties,

indexers, and eventsindexers, and events

 Private interface implementationsPrivate interface implementations

interface interface IDataBoundIDataBound {{ voidvoid Bind(IDataBinderBind(IDataBinder binder);binder); }}

classclass EditBox:EditBox: (^) Control,Control, (^) IDataBoundIDataBound {{ voidvoid IDataBound.Bind(IDataBinderIDataBound.Bind(IDataBinder binder)binder) (^) {...}{...} }}

EnumsEnums

 Strongly typedStrongly typed

 No implicit conversions to/from intNo implicit conversions to/from int

 Operators: +, -, ++, --, &, |, ^, ~Operators: +, -, ++, --, &, |, ^, ~

 Can specify underlying typeCan specify underlying type

 Byte, short, int, longByte, short, int, long

enum enum (^) Color:Color: bytebyte {{ RedRed == 1,1, GreenGreen == 2,2, BlueBlue == 4,4, BlackBlack == 0,0, WhiteWhite == RedRed || GreenGreen || Blue,Blue, }}

Unified Type SystemUnified Type System

 Everything is an objectEverything is an object

 All types ultimately inherit from objectAll types ultimately inherit from object

 Any piece of data can be stored,Any piece of data can be stored,

transported, and manipulated with no transported, and manipulated with no

extra work extra work

Stream Stream

MemoryStream MemoryStream FileStreamFileStream

Hashtable Hashtable intint doubledouble

objectobject

Unified Type SystemUnified Type System

 BoxingBoxing

 Allocates box, copies value into itAllocates box, copies value into it

 UnboxingUnboxing

 Checks type of box, copies value outChecks type of box, copies value out

int int ii == 123;123; objectobject oo == i;i; intint (^) jj == (int)o;(int)o; i^123123

o (^123123)

System.Int32 System.Int

j^123123