Trusted Components. Reuse, Contracts and Patterns. Prof. Dr. Bertrand Meyer Dr. Karine Arnout

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1 1 Last update: 2 November 2004 Trusted Components Reuse, Contracts and Patterns Prof. Dr. Bertrand Meyer Dr. Karine Arnout

2 2 Lecture 26: Component model: The.NET example

3 Agenda for today 3 What is.net? C# basics Eiffel for.net

4 What.NET is not? 4 NOT a programming language: C# is not.net and.net is not C# NOT an operating system (yet).

5 What.NET is 5 An open-language platform for enterprise and Web development.

6 The scope of.net 6.NET addresses almost everyone: The general public New user-friendly services Businesses Help improve B2B relationships. Developers Security Programming-language interoperability Component-based development Versioning Memory management

7 The.NET architecture 7 Web services Open interchange formats Frameworks & libraries Specific language compilers Language interoperability Development environment Compilation, execution Underlying platform UDDI, WSDL, Passport XML & SOAP ASP.NET, Windows Forms, Remoting C#, Visual Basic.Net, Managed C++, Cobol, Eiffel for.net Common Language Specification (CLS) Visual Studio.Net Common Language Runtime (CLR) Hardware, Operating system, database system

8 The Common Language Runtime 8 Basic set of mechanisms to execute.net programs. Virtual machine based on internal code: MSIL. MSIL: not interpreted but jitted to native platform. Built-in security mechanisms.

9 The.NET execution model 9

10 .NET specific vocabulary 10 Managed code: Native code for the target platform, intended to run under the control and with the help of the CLR. Ex: C#, Eiffel for.net, Managed C++ Unmanaged code: Native code that doesn t rely on the CLR. Ex: Classic Eiffel, Unmanaged C++

11 The assembly 11 Compiled form of a set of classes The.NET unit of reuse (.exe or.dll ) May be shared or private. Notion of Global Assembly Cache Contain: MSIL code (not binary code) Metadata (interface information) Can be viewed with ILDasm.

12 The Global Assembly Cache 12

13 .NET core assembly (mscorlib.dll) 13

14 .NET libraries (1/2) 14 System Namespace What for? Basic types: Int32, String System.Collections System.Data System.Drawing System.Net System.Runtime.Remoting System.Security Collection types: ArrayList Relational database management GDI graphics Network communications Distributed computing Security features

15 .NET libraries (2/2) 15 Namespace System.Text System.Text.RegularExpressions System.Threading System.Timers System.Web.UI.WebControls System.Windows.Forms What for? ASCII, Unicode, etc. encoding Regular expressions handling Thread support Raising time-controlled events Graphical Web controls Graphical controls: Button See the Reference documentation for more information.

16 Towards new services 16 A (demo) conference registration page

17 Successful registration 17

18 Passing erroneous data 18

19 About this demo 19 Some of what this demo illustrates: ASP.NET (Active Server Pages.NET) Server-side mechanisms, server controls Debugging Web applications like traditional ones Our first C# example Multi-language development (C#, Eiffel for.net)

20 The ASP.NET source 20

21 Multi-language support 21 C++ C# Eiffel... Framework Windows

22 Languages on.net (1/3) 22 Microsoft languages Visual Basic.Net C# Managed C++ Jscript Commercial languages (see next) Research languages (see next)

23 Languages on.net (2/3) 23 Commercial offerings from 3 rd parties: Cobol (Fujitsu) Eiffel for.net (Eiffel Software) Smalltalk (QKS) Java (JUMP program) Perl, Python (ActiveState) APL (Dyadic) Fortran (Fujitsu) Fortran (Salford Software)

24 Languages on.net (3/3) 24 Research languages: CAML (INRIA) Mercury (Melbourne Uni.) Scheme Oberon (ETH, Zürich) Component Pascal (QUT) Haskell (Universities, Microsoft Research UK)

25 Full interoperability 25 Cross-language Inheritance Classes can inherit from each other, regardless of language of origin. No need for wrappers No IDL Debugging sessions In Visual Studio.Net Exceptions

26 Full interoperability: the price to pay 26 Must conform to the.net object model (VOS, Virtual Object System): The type system Object-oriented principles (type, inheritance) Too much for some (non-o-o languages) Too little for some: multiple inheritance (Eiffel) Difficult features: overloading Must observe the Common Language Specification (CLS)

27 Common Language Specification 27 Set of rules more restrictive than the.net object model to determine compatibility. Part of the ECMA standard Three levels: Producer ( framework ) Consumer Extender

28 CLS rules example 28 (Overloading) Methods and events that have the same name must be distinguished by at least one argument type. Producer: Must mark any offending methods/events as non-cls-compliant. Consumer: Need not accept types that violate these rules, except if marked non-compliant. Extender: Need not provide syntax for defining types that violate this rule.

29 The.NET type system 29 Type Value Reference Class Interface Pointer Integer type Built-in Floating type Typed ref Enums Structureequivalent Nameequivalent Boxed value type Boxed enum Userdefined Array Unmanaged Delegate Function Managed

30 Value vs. reference types 30 Value types denote values (simple value or objects). Reference types denote location of values.

31 Simple value vs. object 31 A simple value cannot by itself identify its type. Ex: int32, float 32 A simple value 342 An object carries its own type description. An object Fields Type info 342 "A string"

32 Value vs. reference types 32 Every value type has a corresponding reference type: its boxed version. Some reference types have a corresponding value type: an unboxed version. Limitation: Inheritance and interfaces apply only to reference types. Boxed Unboxed Type info

33 Built-in types 33 bool char int8, int16, int32, int64 unsigned int8, unsigned int16, unsigned int32, unsigned int64 native int, native unsigned int float32, float64 System.object, System.string typedref *not in CLS

34 Agenda for today 34 What is.net? C# basics Eiffel for.net

35 The C# language 35 Simplified version of C++ Benefits from the Java experience The native language of the.net framework

36 C# and Java 36 Object-oriented: classes, objects, dynamic allocation, inheritance, polymorphism, dynamic binding Type-safe by default (no C++ casts) Support for overloading Support for garbage collection No multiple inheritance from classes No genericity

37 C# vs. Java 37 Coherent type system Close integration with other languages Compiler directives Every piece of software is in a class Variables initialized automatically Event-delegate model Properties Exception handling

38 Hello World! in C# 38 using System; public class Hello { static void Main() { Console.WriteLine( Hello World! ); } } Compiler command line: csc Hello.cs

39 Classes 39 A class consists of members: Fields Methods Properties Events

40 Methods 40 Algorithms associated with the class Work on an instance (unless static). Instance calls or virtual calls A virtual method may be overridden in a descendant class. A virtual method may be marked final.

41 Information hiding (1/2) 41 Access every object through the official operations of its interface. Possible member status: Public Private Family: descendant types only Assembly Family and assembly Family or assembly

42 Information hiding (2/2) 42 Direct field modification (e.g. C++, Java): heater.temperature := 19! Proper O-O technique: set_temperature (t: INTEGER) is do if not in_range (t) then -- Error else temperature := t notify_observers end end

43 The.NET solution: Properties 43 public class Heater { private int TemperatureInternal; public int Temperature { } get {return TemperatureInternal;} set { } if (! InRange (value)) { throw new ArgumentException ( Temperature out of range"); } TemperatureInternal = value; NotifyObservers;

44 Events and Delegates 44 Purpose: Event-driven programming A delegate is an object representing a method of a particular class (like function pointer, but typed). Basic methods on delegates: Invoke BeginInvoke EndInvoke Associate one or more delegates with each event. No way to specify closed arguments

45 Setting an event handler 45 Button ClickMe = new Button (); ClickMe.Text = "Click me!"; ClickMe.Location = new System.Drawing.Point (200, 30); ClickMe.Size = new System.Drawing.Size (30, 10); EventHandler MyHandler = new EventHandler (this.buttonclicked); ClickMe.Click += MyHandler; void ButtonClicked (Object sender, EventArgs args) { }

46 The event definition 46 public class Button { public event EventHandler Click; } protected void OnClick (EventArgs e) { if (Click!= null) Click (this, e); }

47 Exception handling 47 Similar to the Java model: try { // code that may cause an exception } catch (ExceptionType exc) { if CanFix() { FixIt(); } else throw new Exception(); } catch (OtherExceptionType exc) { }

48 Agenda for today 48 What is.net? C# basics Eiffel for.net

49 Eiffel for.net 49 Full implementation of Eiffel on.net: Design by Contract Seamlessness of software development Multiple inheritance Genericity Large set of libraries: Eiffel libraries +.NET libraries Directly available in EiffelStudio Integrated into Visual Studio.NET: Eiffel ENViSioN! Smart editor Project clusters browsing

50 Design by Contract on.net 50 Like Eiffel, Eiffel for.net directly enforces Design by Contract, which addresses: Correctness Documentation Debugging and testing Inheritance control Management Eiffel for.net is the sole language on.net to support contracts.

51 Seamlessness of software development 51 Like Eiffel, Eiffel for.net covers the entire software lifecycle. EiffelStudio provides complete reversibility between class text and diagrams.

52 ISE EiffelStudio 52

53 Multiple inheritance and genericity 53 Or how to map non-cls compliant mechanisms on.net while preserving language interoperability?

54 Multiple inheritance on.net (1/2) 54 How Eiffel for.net does it: Taking full advantage of interfaces and namespaces. A B Impl.A Impl.B C Impl.C Shadowing classes with interfaces.

55 Multiple inheritance on.net (2/2) 55 What about class instantiation? A B Create.A Impl.A Impl.B Create.B C Impl.C Create.C

56 Genericity and covariance on.net 56 Eiffel for.net: Supports genericity. Implements a safe variant of covariance (with type checking) detecting catcalls at run-time.

57 Hello World! with Eiffel for.net 57 class HELLO_WORLD create make feature {NONE} -- Initialization make is do end feature -- Constant -- Print Hello_world_message. io.put_string (Hello_world_message) Hello_world_message: STRING is Hello World! -- Hello World! message end

58 Full interoperability on.net (1/4) 58 With C#: public class HelloWorld1 { public static void Main() { HelloWorld sample; sample = Create.HelloWorld.Make(); } }

59 Full interoperability on.net (2/4) 59 With VB.NET: Public Class HelloWorld1 Public Sub Main () Dim sample as HelloWorld sample = Create.HelloWorld.Make() End Sub End Class

60 Full interoperability on.net (3/4) 60 With C#: using System; public class HelloWorld2: Impl.HelloWorld { public static void Main() { HelloWorld sample; sample = new Impl.HelloWorld(); Console.WriteLine ( sample.helloworldmessage()); } }

61 Full interoperability on.net (4/4) 61 With VB.NET: Imports System Public Class HelloWorld2 Inherits Impl.HelloWorld Public Shared Sub Main() Dim h2 as HelloWorld2 h2 = new HelloWorld2() Console.WriteLine (h2.helloworldmessage()) End Sub End Class

62 Eiffel for.net in Visual Studio.NET 62 EiffelStudio and Visual Studio.NET, two complementary development environments: EiffelStudio for possibly multi-platform development in Eiffel only. Visual Studio.NET for multi-language development.

63 Windows Forms and Eiffel for.net 63 Or how to take advantage from.net libraries from an Eiffel for.net project. Demo

64 Web services with Eiffel for.net 64 It is possible to write ASP.NET pages directly in Eiffel for.net. Page Language = Eiffel %> The registration page demo with Eiffel for.net

65 References 65 Karine Arnout: Introduction to Eiffel for.net. CoDe Magazine, Sept/Oct Bertrand Meyer: The.NET Training Course. Prentice Hall, Bertrand Meyer, Raphaël Simon, Emmanuel Stapf: Instant.NET. Prentice Hall, 2002 (in preparation). Microsoft:.NET Reference documentation. l=/library/en-us/cpref/html/cpref_start.asp. Raphaël Simon, Emmanuel Stapf, Bertrand Meyer: Full Eiffel on.net. MSDN, 2002.

66 66 End of lecture 26

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