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Introduction to the Weband .NET

This material is based on the original slides of Dr. Mark Sapossnek, Computer Science Department, Boston University, Mosh Teitelbaum, evoch, LLC, and Joe Hummel, Lake Forest College

Outline

Internet Technologies

Programming Web & Distributed Applications

.NET Overview

Internet Technologies The World Wide Web

A way to access and share informationTechnical papers, marketing materials, recipes, ...

A huge network of computers: the InternetGraphical, not just textualInformation is linked to other informationApplication development platform

Shop from homeProvide self-help applications for customers and partners...

Internet TechnologiesWWW Architecture

Web Server

PC/Mac/Unix + Browser

Client

Server

Request:http://www.msn.com/default.asp

Response:<html>…</html>

Network TCP/IP

Internet TechnologiesWWW Architecture

Client/Server, Request/Response architectureYou request a Web page

e.g. http://www.msn.com/default.asp

HTTP request

The Web server responds with data in the form of a Web pageHTTP response

Web page is expressed as HTML

Pages are identified as a Uniform Resource Locator (URL)Protocol: http

Web server: www.msn.com

Web page: default.asp

Can also provide parameters: ?name=Keith

Internet TechnologiesWeb Standards

Internet Engineering Task Force (IETF)http://www.ietf.org/

Founded 1986

Request For Comments (RFC) at http://www.ietf.org/rfc.html

World Wide Web Consortium (W3C)http://www.w3.org

Founded 1994 by Tim Berners-Lee

Publishes technical reports and recommendations

Internet TechnologiesHypertext Markup Language (HTML)

The markup language used to represent Web pages for viewing by people

Designed to display data, not store/transfer data

Rendered and viewed in a Web browserCan contain links to images, documents, and other pagesNot extensibleDerived from Standard Generalized Markup Language (SGML)HTML 3.2, 4.01, XHTML 1.0

Internet TechnologiesHTML Forms

Enables you to create interactive user interface elements

Buttons

Text boxes

Drop down lists

Check boxes

User fills out the form and submits it

Form data is sent to the Web server via HTTP when the form is submitted

Internet TechnologiesHypertext Transport Protocol (HTTP)

The top-level protocol used to request and return data

E.g. HTML pages, GIFs, JPEGs, Microsoft Word documents, Adobe PDF documents, etc.

Request/Response protocol

Methods: GET, POST, …

HTTP 1.0: simple

HTTP 1.1: more complex

GET /default.asp HTTP/1.0Accept: image/gif, image/x-bitmap, image/jpeg, */*Accept-Language: enUser-Agent: Mozilla/1.22 (compatible; MSIE 2.0; Windows 95)Connection: Keep-AliveIf-Modified-Since: Sunday, 17-Apr-96 04:32:58 GMT

Internet TechnologiesHTTP Request

Method File HTTP version Headers

Data – none for GET

Blank line

HTTP/1.0 200 OKDate: Sun, 21 Apr 1996 02:20:42 GMTServer: Microsoft-Internet-Information-Server/5.0 Connection: keep-aliveContent-Type: text/htmlLast-Modified: Thu, 18 Apr 1996 17:39:05 GMTContent-Length: 2543

<HTML> Some data... blah, blah, blah </HTML>

Internet TechnologiesHTTP Response

HTTP version Status code Reason phrase Headers

Data

Internet TechnologiesHTTP Server Status Codes

DescriptionCode

Internal Server Error500

Not Found404

Forbidden – not authorized403

Unauthorized401

Bad Request – not understood400

Moved Temporarily302

Moved Permanently301

Created201

OK200

Internet TechnologiesHTTP

HTTP is a stateless protocol

Each HTTP request is independent of previous and subsequent requests

Statelessness has a big impact on how scalable applications are designed

Internet TechnologiesCookies

A mechanism to store a small amount of information (up to 4KB) on the client

A cookie is associated with a specific web site

Cookie is sent in HTTP header

Cookie is sent with each HTTP request

Can last for only one session (until browser is closed) or can persist across sessions

Can expire some time in the future

Internet TechnologiesHTTPS

A secure version of HTTP

Allows client and server to exchange data with confidence that the data was neither modified nor intercepted

Uses Secure Sockets Layer (SSL)/Transport Layer Security (TLS)

Internet TechnologiesURIs, URLs and URNs

Uniform Resource Identifier (URI = URL or URN)Generic term for all textual names/addresses

Uniform Resource Locator (URL)The set of URI schemes that have explicit instructions on how to access the resource over the Internet, e.g. http, ftp, gopher

Uniform Resource Name (URN) 1) A URI that has an institutional commitment to

availability, etc.2) A particular scheme intended to identify resources

e.g. urn:schemas:httpmail:subject

Internet TechnologiesMultipurpose Internet Mail Extensions (MIME)

Defines types of data/documentstext/plain

text/html

image/gif

image/jpeg

audio/x-pn-realaudio

audio/x-ms-wma

video/x-ms-asf

application/octet-stream

Internet TechnologiesMIME

Specifies character sets, e.g. ASCII

Supports multi-part messages

Originally designed for email, but also used in other places, such as HTTP

Internet TechnologiesNetworks - Application Layer

Telnet: Remote sessions

File Transfer Protocol (FTP)

Network News Transfer Protocol (NNTP)

Simple Network Management Protocol (SNMP)

Simple Mail Transfer Protocol (SMTP)

Post Office Protocol (POP3)

Interactive Mail Access Protocol (IMAP)

Internet TechnologiesExtensible Markup Language (XML)

Represents hierarchical data

A meta-language: a language for defining other languages

Extensible

Useful for data exchange and transformation

Simplified version of SGML

Outline


Programming the Web

.NET Overview

Programming the WebClient-Side Code

What is client-side code?Software that is downloaded from Web server to browser and then executes on the client

Why client-side code?Better scalability: less work done on serverBetter performance/user experienceCreate UI constructs not inherent in HTML

Drop-down and pull-out menusTabbed dialogs

Cool effects, e.g. animationData validation

DHTML• DHTML = Dynamic HTML

It allows you to build rich client interfaces and to modifythem dynamically

• There is no DHTML standardIt is not a W3C, IEEE, ISO or anything else standard

• DHTML is a collection of several standardsDHTML consists of HTML/XHTML, CSS, DOM andJavaScript (or ECMAScript)

Programming the WebServer-Side Code

What is server-side code?Software that runs on the server, not the client

Receives input fromURL parameters

HTML form data

Cookies

HTTP headers

Can access server-side databases, e-mail servers, files, mainframes, etc.

Dynamically builds a custom HTML response for a client

Programming the WebServer-Side Code

Why server-side code?Accessibility

You can reach the Internet from any browser, any device, any time, anywhere

ManageabilityDoes not require distribution of application codeEasy to change code

SecuritySource code is not exposedOnce user is authenticated, can only allow certain actions

ScalabilityWeb-based 3-tier architecture can scale out

Programming the WebServer-Side Technologies

Common Gateway Interface (CGI)

Internet Server API (ISAPI)

Netscape Server API (NSAPI)

Active Server Pages (ASP)

Java Server Pages (JSP)

Personal Home Page (PHP)

Cold Fusion (CFM)

ASP.NET

Programming the WebServer-Side Programming

HTTP request(form data, HTTP

header data)

HTTP responseHTML, XML

(static HTML, server-side logic)

Outline


Programming Languages and Paradigms

Programming the Web

.NET Overview

.NET Overview

Introduction to .NET

Web Services

The .NET Framework

Common Language Runtime

Windows Forms

Web Forms

ADO.NET

Languages

Introduction to .NETWhat is .NET?

A vision of how information technology will evolve

A platform that supports the vision

A business model of software as a service


A visionWeb sites will be joined by Web services

New smart devices will join the PC

User interfaces will become more adaptable and customizable

Enabled by Web standards

A platformThe .NET FrameworkVisual Studio.NET.NET Enterprise Servers

Database, Messaging, Integration, Commerce, Proxy, Security, Mobility, Content Management

.NET Web Services as Building BlocksGoal: make it incredibly easy to build powerful Web applications and Web services


A business modelSoftware as a service

Subscription-based services

Application hosting, e.g. bCentral


Introduction to .NETThe .NET Platform

Web Form

.NET Framework

Windows

Web Service

.NET FoundationWeb Services

Your InternalWeb Service

Third-PartyWeb Services

.NET EnterpriseServers

Clients Applications

Protocols: HTTP,HTML, XML, SOAP, UDDI

Tools:Visual Studio.NET,

Notepad

Web Services

A programmable application component accessible via standard Web protocols

The center of the .NET architecture

Exposes functionality over the Web

Built on existing and emerging standardsHTTP, XML, SOAP, UDDI, WSDL, …

Web ServicesEvolution of the Web

Generation 1Static HTML

HTML

Generation 2Web Applications

HTML

HTML, XML

HTML, XML

Generation 3Web Services

A set of technologies for developing and using components to create:

Web Forms

Web Services

Windows Applications

Supports the software lifecycleDevelopment

Debugging

Deployment

Maintenance

The .NET FrameworkWhat Is the .NET Framework?

Common Language Specification

Common Language Runtime

VB C++ C#

ASP.NET: Web Servicesand Web Forms

JScript …

WindowsForms

.NET Framework Base Classes

ADO.NET: Data and XML

Visu

al Stu

dio

.NE

T

The .NET FrameworkThe .NET Framework and Visual Studio.NET

System.Data

DesignOLEDB

SQLTypesSQL

System

GlobalizationDiagnostics

ConfigurationCollections

ResourcesReflection

NetIO

ThreadingText

ServiceProcessSecurity Runtime

InteropServicesRemotingSerialization

System.Xml

XPathXSLT Serialization

System.Web

Configuration SessionStateCaching Security

ServicesDescriptionDiscoveryProtocols

UIHtmlControls

WebControlsSystem.Drawing

ImagingDrawing2D

TextPrinting

The .NET Framework.NET Framework Classes

System.Windows.FormsForm Button

MessageBox ListControl

Common Language RuntimeGoals

Development servicesDeep cross-language interoperabilityIncreased productivity

Deployment servicesSimple, reliable deploymentFewer versioning problems – NO MORE ‘DLL HELL’

Run-time servicesPerformance Scalability Availability

Reliability

Security

Safety

Source Code

C++, C#, VB or any .NET language

csc.exe or vbc.exe

Compiler

Assembly

DLL or EXE

Common Language RuntimeCompilation

AssemblyLogical unit of deployment

Contains Manifest, Metadata, MSIL and resources

ManifestMetadata about the components in an assembly (version, types, dependencies, etc.)

Type MetadataCompletely describes all types defined in an assembly: properties, methods, arguments, return values, attributes, base classes, …

Common Language RuntimeAssemblies

Common Language RuntimeAssemblies

Microsoft Intermediate Language (MSIL, IL)All languages compile to IL (managed code)

IL is always compiled to native code before being executed

ResourcesE.g. .bmp, .jpg

Common Language RuntimeExecution Model

CLR

VBSource code

Compiler

C++C#

Assembly AssemblyAssembly

Operating System Services

MSIL

Common Language Runtime JIT Compiler

Compiler Compiler

Nativecode

ManagedCode

ManagedCode

ManagedCode

UnmanagedCode

CLR Services

Ngen

Assemblies

1 assembly = 1 or more compiled classes.EXE represents an assembly with classes + Main program

.DLL represents an assembly with classes

Development Tools

assembly

code.vbcode.vb

code.cs

.EXE / .DLL

.NET development

There are currently 3 ways to develop assemblies:

1) .NET Framework SDKfree (100 MB)

complete set of command-line tools and docs

available for Windows NT, 2000, XP Pro, 2003

http://msdn.microsoft.com/net

other platforms?FreeBSD / Mac OS X via Rotor (i.e. SSCLI)

Linux via Mono project

Development options, cont'd

2) Visual Studio .NET5-6 CDs, 192 MB RAM (bare minimum)

powerful, integrated development environment (IDE)

one IDE for all: GUI, web-based, web service, DLLs, etc.

this is what 99% of the world uses

$$MSDNAA reduces cost to $800/year for unlimited access

3) free IDEs#develop, a simplified clone of VS.NET

WebMatrix, for building web-based applications

Hello World in C#

Here's the source code:

/* hello.cs */

public class Startup{

public static void Main(){

System.Console.WriteLine("Hello World!");}

}//class

hello.cs

Why System.Consoleprefix?

In .NET, all code & data must live within a module / class

Often nested within namespaces to help organize thingsa namespace is really just a named collection

Example: System.Console.WriteLine("Hello World!");

Consoleclass

WriteLinesubroutine

Systemnamespace

in FCL

Compiling and running

To compile C# with Framework SDK, use the C# compiler

open Visual Studio .NET command prompt window to set path

csc is the command-line C# compiler

use /t:exe option to specify console-based EXE as target

c:\> csc /t:exe hello.csMicrosoft (R) Visual C# .NET Compiler version 7.00.9466for Microsoft (R) .NET Framework version 1.0.3705Copyright (C) Microsoft Corporation 2001. All rights reserved.

c:\> hello.exeHello World!

Viewing an assembly with ILDasm

IL = Microsoft's Intermediate Language (i.e. generic asm)

ILDasm = IL Disassembler

c:\> ildasm hello.exe

IL?

Very similar to Java bytecodes:generic assembly language

stack-based

strictly typed

no direct memory addressing

verifiable for safe execution

Development on FreeBSD

Working on FreeBSD is exactly the same!i.e. same command-line tools as Framework SDK

produces *binary-compatible* .DLL and .EXE files!

Class-based development: Example

Here's the source code for a simple Customer class:

/* customer.cs */

public class Customer{

public string Name; // fieldspublic int ID;

public Customer(string name, int id) // constructor{this.Name = name;this.ID = id;

}

public override string ToString() // method{return "Customer: " + this.Name;

}}//class

Main class

Here's the source code for Main, using our Customer class:

/* main.cs */

public class App{

public static void Main(){

Customer c;c = new Customer("joe hummel", 94652);System.Console.WriteLine( c.ToString() );

}

}//class

Compiling and running application

Compile and run as before…/out: option specifies name of resulting EXE

in this case we are building monolithic app (single EXE, no DLLs)

c:\> csc /t:exe /out:app.exe main.cs customer.csMicrosoft (R) Visual C# .NET Compiler version 7.00.9466for Microsoft (R) .NET Framework version 1.0.3705Copyright (C) Microsoft Corporation 2001. All rights reserved.

c:\> app.exeCustomer: joe hummel

Component-based development: Example

Let's rebuild previous app based on componentsCustomer class ==> DLL

Main class ==> EXE

app.exe customer.dll+

main.cs customer.cs

Compiling a component

Use the C# compiler…with /t:library option to specify component library as target

csc produces a DLL in this case

c:\> csc /t:library customer.csMicrosoft (R) Visual C# .NET Compiler version 7.00.9466for Microsoft (R) .NET Framework version 1.0.3705Copyright (C) Microsoft Corporation 2001. All rights reserved.

c:\> dir *.dllcustomer.dll

Compiling and running application

Compile using C# compiler as before, except…reference component so compiler can locate Customer class!

reference also stored inside assembly so CLR can locate

To run, use name of assembly containing Main…CLR follows reference to locate DLL

c:\> csc /t:exe /out:app.exe main.cs /r:customer.dllMicrosoft (R) Visual C# .NET Compiler version 7.00.9466for Microsoft (R) .NET Framework version 1.0.3705Copyright (C) Microsoft Corporation 2001. All rights reserved.

c:\> app.exeCustomer: joe hummel

Where are references stored?

Within assembly as part of assembly manifest

Visible via ILDasmc:\> ildasm app.exe

mscorlib?

mscorlib = "ms-core-lib"

Core FCL assemblycontains core system classes like string

contains System.Console class for console-based I/O

Automatically referenced for us by C# compiler…

All assemblies must be present

.EXE

other FCL assemblies

CLR

JIT Compiler

obj code

OS Process

Underlying OS and HW

Core FCLassembly

.DLL.DLL

.DLL

obj codeobj code

obj code

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