Trusted Components Reuse, Contracts and Patterns Prof. Dr. Bertrand - - PowerPoint PPT Presentation

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1 Last update: 2 November 2004 Trusted Components Reuse, Contracts and Patterns Prof. Dr. Bertrand Meyer Dr. Karine Arnout Chair of Softw are Engineering Trusted Components: Reuse, Contracts and Patterns - Lecture 26 2 Lecture 26:

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Chair of Softw are Engineering

Last update: 2 November 2004

Trusted Components

Reuse, Contracts and Patterns

  • Prof. Dr. Bertrand Meyer
  • Dr. Karine Arnout
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Lecture 26: Component model: The .NET example

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Agenda for today

  • What is .NET?
  • C# basics
  • Eiffel for .NET
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What .NET is not?

  • NOT a programming language:
  • “C# is not .NET and .NET is not C# ”
  • NOT an operating system (yet).
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What .NET is…

An open-language platform for enterprise and Web development.

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The scope of .NET

.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

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The .NET architecture

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

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The Common Language Runtime

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.

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The .NET execution model

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.NET specific vocabulary

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+ +

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The assembly

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.

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The Global Assembly Cache

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.NET core assembly (mscorlib.dll)

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.NET libraries (1/ 2)

Nam espace W hat for?

System Basic types: Int32, String … System.Collections Collection types: ArrayList… System.Data Relational database management System.Net Network communications System.Security Security features System.Runtime.Remoting Distributed computing System.Drawing GDI graphics

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.NET libraries (2/ 2)

Nam espace W hat for?

System.Text ASCII, Unicode, etc. encoding System.Threading Thread support System.Timers Raising time-controlled events System.Text.RegularExpressions Regular expressions handling System.Web.UI.WebControls Graphical Web controls System.Windows.Forms Graphical controls: Button…

→ See the Reference documentation for more information.

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Towards new services…

A (demo) conference registration page

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Successful registration

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Passing erroneous data

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About this demo…

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)

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The ASP.NET source

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Multi-language support

C++ C# Eiffel Framework

...

Windows

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Languages on .NET (1/ 3)

“Microsoft languages” Visual Basic.Net C# Managed C+ + Jscript Commercial languages (see next) Research languages (see next)

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Languages on .NET (2/ 3)

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

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Languages on .NET (3/ 3)

Research languages: CAML (INRIA) Mercury (Melbourne Uni.) Scheme Oberon (ETH, Zürich) Component Pascal (QUT) Haskell (Universities, Microsoft Research UK)

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Full interoperability

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

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Full interoperability: the price to pay…

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)

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Common Language Specification

Set of rules – more restrictive than the .NET object model – to determine compatibility. Part of the ECMA standard Three levels: Producer (“framework”) Consumer Extender

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CLS rules example

(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.

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The .NET type system

Reference Value Built-in Floating type Typed ref Integer type User- defined Enums Pointer Managed Unmanaged Function Interface Type Class Structure- equivalent Boxed enum Array Delegate Name- equivalent Boxed value type

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Value vs. reference types

Value types denote values (simple value or

  • bjects).

Reference types denote location of values.

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Simple value vs. object

A simple value cannot by itself identify its type. Ex: int32, float 32 An object carries its

  • wn type description.

Type info Fields 342 "A string" 342

An object

A simple value

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Value vs. reference types

  • 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

  • nly

to reference types.

Type info 342

Boxed

342

Unboxed

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Built-in types

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

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Agenda for today

  • What is .NET?
  • C# basics
  • Eiffel for .NET
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The C# language

“Simplified version of C+ + ” Benefits from the Java experience The native language of the .NET framework

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C# and Java

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

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C# vs. Java

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

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“Hello World!” in C#

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

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Classes

A class consists of members: Fields Methods Properties Events

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Methods

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.

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Information hiding (1/ 2)

Access every object through the official

  • perations of its interface.

Possible member status: Public Private Family: descendant types only Assembly Family and assembly Family or assembly

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Information hiding (2/ 2)

!

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

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The .NET solution: Properties

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; } }

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Events and Delegates

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

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Setting an event handler

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) { … }

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The event definition

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

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Exception handling

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) { … }

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Agenda for today

  • What is .NET?
  • C# basics
  • Eiffel for .NET
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Eiffel for .NET

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…

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Design by Contract on .NET

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.

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Seamlessness of software development

Like Eiffel, Eiffel for .NET covers the entire software lifecycle. EiffelStudio provides complete reversibility between class text and diagrams.

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ISE EiffelStudio

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Multiple inheritance and genericity…

… Or how to map non-CLS compliant mechanisms on .NET while preserving language interoperability?

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Multiple inheritance on .NET (1/ 2)

How Eiffel for .NET does it: Taking full advantage of interfaces and namespaces.

A Impl.A B Impl.B C Impl.C

Shadowing classes with interfaces.

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Multiple inheritance on .NET (2/ 2)

What about class instantiation?

A Impl.A B Impl.B C Impl.C Create.A Create.C Create.B

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Genericity and covariance on .NET

Eiffel for .NET: Supports genericity. Implements a safe variant of covariance (with type checking) detecting catcalls at run-time.

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“Hello World!” with Eiffel for .NET

class HELLO_WORLD create make feature { NONE} -- Initialization make is

  • - Print Hello_world_message.

do io.put_string (Hello_world_message) end feature -- Constant Hello_world_message: STRING is “Hello World!”

  • - Hello World! message

end

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Full interoperability on .NET (1/ 4)

With C# : public class HelloWorld1 { public static void Main() { HelloWorld sample; sample = Create.HelloWorld.Make(); } }

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Full interoperability on .NET (2/ 4)

With VB.NET: Public Class HelloWorld1 Public Sub Main () Dim sample as HelloWorld sample = Create.HelloWorld.Make() End Sub End Class

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Full interoperability on .NET (3/ 4)

With C# : using System; public class HelloWorld2: Impl.HelloWorld { public static void Main() { HelloWorld sample; sample = new Impl.HelloWorld(); Console.WriteLine ( sample.HelloWorldMessage()); } }

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Full interoperability on .NET (4/ 4)

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

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Eiffel for .NET in Visual Studio.NET

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.

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Windows Forms and Eiffel for .NET

… Or how to take advantage from .NET libraries from an Eiffel for .NET project. Dem o

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Web services with Eiffel for .NET

It is possible to write ASP.NET pages directly in Eiffel for .NET. < % @ Page Language = “Eiffel” % > The registration page dem o w ith Eiffel for .NET

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References

  • Karine Arnout: Introduction to Eiffel for .NET.

CoDe Magazine, Sept/ Oct 2002.

  • Bertrand Meyer: The .NET Training Course.

Prentice Hall, 2001.

  • Bertrand Meyer, Raphaël Simon, Emmanuel

Stapf: Instant .NET. Prentice Hall, 2002 (in preparation).

  • Microsoft: .NET Reference documentation.

http: / / msdn.microsoft.com/ library/ default.asp?ur l= / library/ en-us/ cpref/ html/ cpref_start.asp.

  • Raphaël Simon, Emmanuel Stapf, Bertrand

Meyer: Full Eiffel on .NET. MSDN, 2002.

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End of lecture 26