Introduction to Csharp

Introduction to C# Introduction to C# Anders Anders HejlsbergHejlsberg Distinguished EngineerDistinguished Engineer Developer DivisionDeveloper Division Microsoft CorporationMicrosoft Corporation C# C# –– The Big IdeasThe Big Ideas „„ The first component oriented The 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 and Next generation robust and durable softwaredurable software „„ Preservation of investmentPreservation of investment C# C# –– The Big IdeasThe Big Ideas A component oriented languageA component oriented language „„ C# is the first “component oriented” C# is the first “component oriented” language in the C/C++ familylanguage in the C/C++ family „„ Component concepts are first class:Component concepts are first class: †† Properties, methods, eventsProperties, methods, events †† DesignDesign--time and runtime and run--time attributestime attributes †† Integrated documentation using XMLIntegrated documentation using XML „„ Enables oneEnables one--stop programmingstop programming †† No header files, IDL, etc.No header files, IDL, etc. †† Can be embedded in web pagesCan be embedded in web pages C# C# –– The Big IdeasThe Big Ideas Everything really is an objectEverything really is an object „„ Traditional viewsTraditional views †† C++, Java: Primitive types are “magic” and do C++, Java: Primitive types are “magic” and do not interoperate with objectsnot interoperate with objects †† Smalltalk, Lisp: Primitive types are objects, but Smalltalk, 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 Collections, etc., work for all all typestypes C# C# –– The Big IdeasThe Big Ideas Robust and durable softwareRobust 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 „„ TypeType--safetysafety †† No No uninitializeduninitialized variables, unsafe castsvariables, unsafe casts „„ VersioningVersioning †† Pervasive versioning considerations in Pervasive versioning considerations in all aspects of language designall aspects of language design C# C# –– The Big IdeasThe Big Ideas Preservation of InvestmentPreservation of Investment „„ C++ heritageC++ heritage †† Namespaces, Namespaces, enumsenums, unsigned types, pointers , unsigned types, pointers (in unsafe code), etc.(in unsafe code), etc. †† No unnecessary sacrificesNo unnecessary sacrifices „„ InteroperabilityInteroperability †† What software is increasingly aboutWhat software is increasingly about †† MS C# implementation talks to XML, SOAP, MS C# implementation talks to XML, SOAP, COM, DLLs, and any .NET languageCOM, DLLs, and any .NET language „„ Millions of lines of C# code in .NETMillions of lines of C# code in .NET †† Short learning curveShort learning curve †† Increased productivityIncreased productivity Hello WorldHello World using System;using System; class Helloclass Hello {{ static void Main() {static void Main() { Console.Console.WriteLineWriteLine("Hello world");("Hello world"); }} }} C# Program StructureC# Program Structure „„ NamespacesNamespaces †† Contain types and other namespacesContain types and other namespaces „„ Type declarationsType declarations †† Classes, Classes, structsstructs, interfaces, , interfaces, enumsenums, , 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 “inNo header files, code written “in--line”line” †† No declaration order dependenceNo declaration order dependence C# Program StructureC# Program Structure using System;using System; namespace System.Collectionsnamespace System.Collections {{ public class Stackpublic class Stack {{ Entry top;Entry top; public void Push(object data) {public void Push(object data) { top = new Entry(top, data);top = new Entry(top, data); }} public object Pop() {public object Pop() { if (top == null) throw new if (top == null) throw new InvalidOperationExceptionInvalidOperationException();(); object result = top.data;object result = top.data; top = top.next;top = top.next; return result;return result; }} }} }} 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 intint i = 123;i = 123; string s = "Hello world";string s = "Hello world"; ii 123123 ss "Hello world""Hello world" Type SystemType System „„ Value typesValue types †† PrimitivesPrimitives intint i;i; †† EnumsEnums enumenum State { Off, On }State { Off, On } †† StructsStructs structstruct Point {Point { intint x, y; }x, y; } „„ Reference typesReference types †† ClassesClasses class Foo: Bar,class Foo: Bar, IFooIFoo {...}{...} †† InterfacesInterfaces interface interface IFooIFoo:: IBarIBar {...}{...} †† ArraysArrays string[] a = new string[10];string[] a = new string[10]; †† DelegatesDelegates delegate void Empty();delegate void Empty(); Predefined TypesPredefined Types „„ C# predefined typesC# predefined types †† ReferenceReference object, stringobject, string †† SignedSigned sbytesbyte, short,, short, intint, long, long †† Unsigned Unsigned byte,byte, ushortushort,, uintuint, , ulongulong †† CharacterCharacter charchar †† FloatingFloating--pointpoint float, double, decimalfloat, double, decimal †† LogicalLogical boolbool „„ Predefined types are simply aliases Predefined types are simply aliases for systemfor system--provided typesprovided types †† For example,For example, intint == System.Int32== System.Int32 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 inStored in--line, not heap allocatedline, 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 †† intint, float, double, etc., are all , float, double, etc., are all structsstructs „„ BenefitsBenefits †† No heap allocation, less GC pressureNo heap allocation, less GC pressure †† More efficient use of memoryMore efficient use of memory Classes And Classes And StructsStructs class class CPointCPoint {{ intint x, y; ... }x, y; ... } structstruct SPoint SPoint { { int int x, y; ... }x, y; ... } CPointCPoint cp = new cp = new CPointCPoint(10, 20);(10, 20); SPointSPoint sp = new sp = new SPointSPoint(10, 20);(10, 20); 1010 spsp 2020 cpcp 1010 2020 CPointCPoint 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 {{ void Bind(void Bind(IDataBinder IDataBinder binder);binder); }} class class EditBoxEditBox: Control, : Control, IDataBoundIDataBound {{ void void IDataBoundIDataBound.Bind(.Bind(IDataBinder IDataBinder binder) {...}binder) {...} }} EnumsEnums „„ Strongly typedStrongly typed †† No implicit conversions to/from No implicit conversions to/from intint †† Operators: +, Operators: +, --, ++, , ++, ----, &, |, ^, ~, &, |, ^, ~ „„ Can specify underlying typeCan specify underlying type †† Byte, short, Byte, short, intint, long, long enum enum Color: byteColor: byte {{ Red = 1,Red = 1, Green = 2,Green = 2, Blue = 4,Blue = 4, Black = 0,Black = 0, White = Red | Green | Blue,White = Red | Green | Blue, }} DelegatesDelegates „„ Object oriented function pointersObject oriented function pointers „„ Multiple receiversMultiple receivers †† Each delegate has an invocation listEach delegate has an invocation list †† ThreadThread--safe + and safe + and -- operationsoperations „„ Foundation for eventsFoundation for events delegate voiddelegate void MouseEventMouseEvent((intint x,x, intint y);y); delegate doubledelegate double FuncFunc(double x);(double x); Func funcFunc func = new= new FuncFunc(Math.Sin);(Math.Sin); double x =double x = funcfunc(1.0);(1.0); 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 workextra work StreamStream MemoryStreamMemoryStream FileStreamFileStream HashtableHashtable doubledoubleintint 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 intint i = 123;i = 123; object o = i;object o = i; intint j = (j = (intint)o;)o; 123123i System.Int32System.Int32o 123123 123123j Unified Type SystemUnified Type System „„ BenefitsBenefits †† Eliminates “wrapper classes”Eliminates “wrapper classes” †† Collection classes work with all typesCollection classes work with all types †† Replaces OLE Automation's VariantReplaces OLE Automation's Variant „„ Lots of examples in .NET FrameworkLots of examples in .NET Framework string s = string.Format(string s = string.Format( "Your total was {0} on {1}", total, date);"Your total was {0} on {1}", total, date); HashtableHashtable t = newt = new HashtableHashtable();(); t.Add(0, "zero");t.Add(0, "zero"); t.Add(1, "one");t.Add(1, "one"); t.Add(2, "two");t.Add(2, "two"); Component DevelopmentComponent Development „„ What defines a component?What defines a component? †† Properties, methods, eventsProperties, methods, events †† Integrated help and documentationIntegrated help and documentation †† DesignDesign--time informationtime information „„ C# has first class supportC# has first class support †† Not naming patterns, adapters, etc.Not naming patterns, adapters, etc. †† Not external filesNot external files „„ Components are easy to build Components are easy to build and consumeand consume PropertiesProperties „„ Properties are “smart fields”Properties are “smart fields” †† Natural syntax, Natural syntax, accessorsaccessors, , inlininginlining public class Button: Controlpublic class Button: Control {{ private string caption;private string caption; public string Caption {public string Caption { get {get { return caption;return caption; }} set {set { caption = value;caption = value; Repaint();Repaint(); }} }} }} Button b = new Button();Button b = new Button(); b.Caption = "OK";b.Caption = "OK"; String s = b.Caption;String s = b.Caption; IndexersIndexers „„ Indexers are “smart arrays”Indexers are “smart arrays” †† Can be overloadedCan be overloaded public classpublic class ListBoxListBox: Control: Control {{ private string[] items;private string[] items; public string this[public string this[intint index] {index] { get {get { return items[index];return items[index]; }} set {set { items[index] = value;items[index] = value; Repaint();Repaint(); }} }} }} ListBox listBoxListBox listBox = new = new ListBoxListBox();(); listBoxlistBox[0] = "hello";[0] = "hello"; Console.Console.WriteLineWriteLine((listBoxlistBox[0]);[0]); Events Events SourcingSourcing „„ Define the event signatureDefine the event signature „„ Define the event and firing logicDefine the event and firing logic public delegate void public delegate void EventHandlerEventHandler(object sender, (object sender, EventArgsEventArgs e);e); public class Buttonpublic class Button {{ public eventpublic event EventHandlerEventHandler Click;Click; protected voidprotected void OnClickOnClick((EventArgsEventArgs e) {e) { if (Click != null) Click(this, e);if (Click != null) Click(this, e); }} }} Events Events HandlingHandling „„ Define and register event handlerDefine and register event handler public class public class MyFormMyForm: Form: Form {{ Button Button okButtonokButton;; public public MyFormMyForm() {() { okButton okButton = new Button(...);= new Button(...); okButtonokButton.Caption = "OK";.Caption = "OK"; okButtonokButton.Click += new .Click += new EventHandlerEventHandler((OkButtonClickOkButtonClick);); }} void void OkButtonClickOkButtonClick(object sender, (object sender, EventArgs EventArgs e) {e) { ShowMessageShowMessage("You pressed the OK button");("You pressed the OK button"); }} }} AttributesAttributes „„ How do you associate information How do you associate information with types and members?with types and members? †† Documentation URL for a classDocumentation URL for a class †† Transaction context for a methodTransaction context for a method †† XML persistence mappingXML persistence mapping „„ Traditional solutionsTraditional solutions †† Add keywords or Add keywords or pragmaspragmas to languageto language †† Use external files, e.g., .IDL, .DEFUse external files, e.g., .IDL, .DEF „„ C# solution: AttributesC# solution: Attributes AttributesAttributes public class public class OrderProcessorOrderProcessor {{ [[WebMethodWebMethod]] public void public void SubmitOrderSubmitOrder((PurchaseOrder PurchaseOrder order) {...}order) {...} }} [[XmlRootXmlRoot("Order", Namespace="urn:acme.b2b("Order", Namespace="urn:acme.b2b--schema.v1")]schema.v1")] public class public class PurchaseOrderPurchaseOrder {{ [[XmlElementXmlElement("("shipToshipTo")] public Address ")] public Address ShipToShipTo;; [[XmlElementXmlElement("("billTobillTo")] public Address ")] public Address BillToBillTo;; [[XmlElementXmlElement("comment")] public string Comment;("comment")] public string Comment; [[XmlElementXmlElement("items")] public Item[] Items;("items")] public Item[] Items; [[XmlAttributeXmlAttribute("date")] public ("date")] public DateTime OrderDateDateTime OrderDate;; }} public class Address {...}public class Address {...} public class Item {...}public class Item {...} AttributesAttributes „„ Attributes can beAttributes can be †† Attached to types and membersAttached to types and members †† Examined at runExamined at run--time using reflectiontime using reflection „„ Completely extensibleCompletely extensible †† Simply a class that inherits from Simply a class that inherits from System.AttributeSystem.Attribute „„ TypeType--safesafe †† Arguments checked at compileArguments checked at compile--timetime „„ Extensive use in .NET FrameworkExtensive use in .NET Framework †† XML, Web Services, security, serialization, XML, Web Services, security, serialization, component model, COM and P/Invoke interop, component model, COM and P/Invoke interop, code configuration…code configuration… XML CommentsXML Comments classclass XmlElementXmlElement {{ ///

///

/// Returns the attribute with the given name and/// Returns the attribute with the given name and /// namespace

/// namespace

/// name="name"> /// The name of the attribute> /// name="ns"> /// The namespace of the attribute, or null if/// The namespace of the attribute, or null if /// the attribute has no namespace> /// /// /// The attribute value, or null if the attribute/// The attribute value, or null if the attribute /// does not exist/// does not exist /// (string)"/> ////// public stringpublic string GetAttrGetAttr(string name, string ns) {(string name, string ns) { ...... }} }} Statements And Statements And ExpressionsExpressions „„ High C++ fidelityHigh C++ fidelity „„ If, while, do requireIf, while, do require boolbool conditioncondition „„ gotogoto can’t jump into blockscan’t jump into blocks „„ Switch statementSwitch statement †† No fallNo fall--through, “through, “gotogoto case” or “case” or “gotogoto default”default” „„ foreachforeach statementstatement „„ Checked and unchecked statementsChecked and unchecked statements „„ Expression statements must do workExpression statements must do work void Foo() {void Foo() { i == 1; // errori == 1; // error }} foreach foreach StatementStatement „„ Iteration of arraysIteration of arrays „„ Iteration of userIteration of user--defined collectionsdefined collections public static void Main(string[] public static void Main(string[] argsargs) {) { foreachforeach (string s in(string s in argsargs) Console.) Console.WriteLineWriteLine(s);(s); }} foreachforeach (Customer c in customers.(Customer c in customers.OrderByOrderBy("name")) {("name")) { if (c.Orders.Count != 0) {if (c.Orders.Count != 0) { ...... }} }} Parameter ArraysParameter Arrays „„ Can write “Can write “printfprintf” style methods” style methods †† TypeType--safe, unlike C++safe, unlike C++ voidvoid printfprintf(string(string fmtfmt,, paramsparams object[]object[] argsargs) {) { foreachforeach (object x in(object x in argsargs) {) { ...... }} }} printfprintf("%s %i %i",("%s %i %i", strstr, int1, int2);, int1, int2); object[]object[] argsargs = new object[3];= new object[3]; argsargs[0] = [0] = strstr;; argsargs[1] = int1;[1] = int1; ArgsArgs[2] = int2;[2] = int2; printfprintf("%s %i %i", ("%s %i %i", argsargs);); Operator OverloadingOperator Overloading „„ First class userFirst class user--defined data typesdefined data types „„ Used in base class libraryUsed in base class library †† Decimal,Decimal, DateTimeDateTime,, TimeSpanTimeSpan „„ Used in UI libraryUsed in UI library †† Unit, Point, RectangleUnit, Point, Rectangle „„ Used in SQL integrationUsed in SQL integration †† SQLStringSQLString, SQLInt16, SQLInt32, , SQLInt16, SQLInt32, SQLInt64,SQLInt64, SQLBoolSQLBool,, SQLMoneySQLMoney,, SQLNumericSQLNumeric, , SQLFloatSQLFloat…… Operator OverloadingOperator Overloading publicpublic struct DBIntstruct DBInt {{ public staticpublic static readonly DBIntreadonly DBInt Null = newNull = new DBIntDBInt();(); privateprivate intint value;value; privateprivate boolbool defined;defined; publicpublic bool IsNullbool IsNull { get { return !defined; } }{ get { return !defined; } } public staticpublic static DBIntDBInt operator +(operator +(DBIntDBInt x,x, DBIntDBInt y) {...}y) {...} public static implicit operatorpublic static implicit operator DBIntDBInt((intint x) {...}x) {...} public static explicit operatorpublic static explicit operator intint((DBIntDBInt x) {...}x) {...} }} DBIntDBInt x = 123;x = 123; DBIntDBInt y =y = DBI