Tài liệu Developing .Net Web Services With Xml ppt

WSDL 15An Overview of the System.Web.ServicesNamespace 17 Chapter 2 Introduction to the Setting the Start Page When testing a Web Service in a project that contains other .aspx or .asmx

s o l u t i o n s @ s y n g r e s s c o m

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KEY SERIAL NUMBER

Developing NET Web Services with XML

Copyright © 2002 by Syngress Publishing, Inc All rights reserved Printed in the United States of America Except as permitted under the Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher, with the exception that the program listings may be entered, stored, and executed in a computer system, but they may not be reproduced for publication.

Printed in the United States of America

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ISBN: 1-928994-81-4

Technical Editor: David Jorgensen Cover Designer: Michael Kavish

Acquisitions Editor: Catherine B Nolan Page Layout and Art by: Shannon Tozier

Copy Editor: Adrienne Rebello Indexer: J Edmund Rush

Distributed by Publishers Group West in the United States and Jaguar Book Group in Canada.

Acknowledgments

v

We would like to acknowledge the following people for their kindness and support

in making this book possible

Ralph Troupe, Rhonda St John, Emlyn Rhodes, and the team at Callisma for theirinvaluable insight into the challenges of designing, deploying and supporting world-class enterprise networks

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Contributors

Mesbah Ahmed(PhD and MS, Industrial Engineering) is a Professor ofInformation Systems at the University of Toledo In addition to teachingand research, he provides technical consulting and training for IT andmanufacturing industries in Ohio and Michigan His consulting experi-ence includes systems design and implementation projects with FordMotors, Dana Corporation, Riverside Hospital, Sears, and others

Currently, he provides IT training in the areas of Java Server, XML, and.NET technologies He teaches graduate level courses in DatabaseSystems, Manufacturing Systems, and Application Development inDistributed and Web Environment Recently, he received the University

of Toledo Outstanding Teaching award, and the College of BusinessGraduate Teaching Excellence award His current research interests are inthe areas of data warehousing and data mining He has published many

research articles in academic journals such as Decision Sciences, Information

& Management, Naval Research Logistic Quarterly, Journal of Operations Management, IIE Transaction, and International Journal of Production Research.

He has also presented numerous papers and seminars in many nationaland international conferences Mesbah is a contributor to Syngress

Publishing’s ASP NET Developer’s Guide (ISBN: 1-928994-51-2).

Patrick Coelho(MCP) is an Instructor at The University of WashingtonExtension, North Seattle Community College, Puget Sound Center, andSeattle Vocational Institute, where he teaches courses in Web

Development (DHTML, ASP, XML, XSLT, C#, and ASP.NET) Patrick is

a Co-Founder of DotThatCom.com, a company that provides consulting,online development resources, and internships for students He is cur-rently working on a NET solution with contributing author DavidJorgensen and nLogix Patrick holds a bachelor’s of Science degree fromthe University of Washington, Bothell Patrick lives in Puyallup,WA withhis wife, Angela Patrick is a contributor to Syngress Publishing’s

ASP.NET Developer’s Guide (ISBN: 1-928994-51-2), C# NET Web Developer’s Guide (ISBN: 1-928994-50-4), and NET Mobile Web Developer’s Guide (ISBN: 1-928994-56-3).

Adrian Turtschi(MCSD, MCSE) was formerly employed by KPMGInternational/CERING as an Integration Architect He was responsiblefor integration of components, services and third-party applications ofKPMG’s next generation global knowledge management and collabora-tion solution (KnewPro) KnewPro is an application supporting collabora-tion between geographically and organizationally distributed teams,integrating knowledge sharing and content management, team collabora-tion, enterprise search, workflow, and legacy data connectivity Adrian alsoco-wrote the KnewPro architecture document Prior to joining KPMG,

he worked for EBSCO Publishing as a Software Engineer Adrian is rienced with Java, C#,Visual Basic, Pascal, and the NET Framework as amember of the Early Adopter program Adrian is a contributor to

expe-Syngress Publishing’s C# NET Web Developer’s Guide (ISBN:

1-928994-50-4) He is fluent in English, French, German, and Italian He has done

presentations and has published articles with XML Journal, Nature, and

Exchange & Outlook Magazine Adrian graduated with a master’s of Science

in Computer Science and Mathematics from the University of Bern,

School of Science, Bern, Switzerland and a master’s of Arts in

Mathematics from Brandeis University, Graduate School of Arts andSciences,Waltham, MA.He resides in Germany

David Jorgensen (MCP) David works for Alliance Enterprises, Inc inOlympia WA, which develops Web-based case management software forsocial service organizations such as state vocational rehabilitation agencies.His latest project; convert a state agencies data, involved complex SQLServer Data Transformation Packages David holds a bachelor’s degree inComputer Science from St Martin’s College and resides in Puyallup,WAwith his wife, Lisa and their two sons, Scott and Jacob David is a contrib-

utor to Syngress Publishing’s C# NET Web Developer’s Guide (ISBN: 1-928994-50-4), and the NET Mobile Web Developer’s Guide

(ISBN: 1-928994-56-3)

Technical Editor and Contributor

WSDL 15

An Overview of the System.Web.ServicesNamespace 17

Chapter 2 Introduction to the

Setting the Start Page

When testing a Web

Service in a project that

contains other aspx or

.asmx files, be sure to set

the file you are debugging

or testing as the Start

page, before running To

do this, right-click the

filename in the Solution

Explorer and select Set as

start page.

Additional Installation Information 33Locations for Downloading 34Installing the NET Framework 34Common Language Runtime 36Major Responsibilities of the CLR 36Safety and Security Checks 37

Object Lifetime Management 37Just In Time (JIT) Compilation 38Cross-Language Interoperability 38Structured Exception Handling 39Assemblies 39Metadata 40Enhanced Deployment and Versioning

Support 41Managed versus Unmanaged Code 41Interoperability with Unmanaged Code 42Namespaces 42Developing Applications with the

Summary 62Solutions Fast Track 63Frequently Asked Questions 65

NT 4.0 server you must

have service pack 6a

applied.

Q: Where can I find the

install for ASP.NET?

A: ASP.NET ships as part

of the NET Framework

SDK.

in VS.NET XML Designer 71Components of an XML Document 72Well-Formed XML Documents 75Schema and Valid XML Documents 76Structure of an XML Document 80Processing XML Documents Using NET 81Reading and Writing XML Documents 82Storing and Processing XML Documents 83Reading and Parsing Using the

XmlTextReader Class 84

Parsing an XML Document 85Navigating through an XML

Document to Retrieve Data 87Writing an XML Document

Using the XmlTextWriter Class 90

Generating an XML Document

Using XmlTextWriter 90Exploring the XML Document Object Model 93

Navigating through an XmlDocument Object 94

Parsing an XML Document

Using the XmlDocument Object 95 Using the XmlDataDocument Class 98 Loading an XmlDocument and

Retrieving the Values of Certain Nodes 99Using the Relational View of

an XmlDataDocument Object 100

Viewing Multiple Tables of

a XmlDataDocument Object 103 Querying XML Data Using XPathDocument

Components of an XML Document

■ Schema or Document Type Definition (DTD)

In certain situations, a schema or DTD may precede the XML document

■ Elements An XML

document is mostly composed of elements.

■ Root Element In an

XML document, one single main element must contain all other elements inside it This specific element is often called the root element.

■ Attributes An

attribute is just an additional way to attach a piece of data

to an element.

Using XPathDocument and

Using XPathDocument and XPathNavigator

Objects for Document Navigation 112Transforming an XML Document Using XSLT 115Transforming an XML Document to

an HTML Document 116Transforming an XML Document

into Another XML Document 119Working with XML and Databases 124Creating an XML Document

from a Database Query 125Reading an XML Document into a DataSet 127Summary 129Solutions Fast Track 129Frequently Asked Questions 133

Chapter 4 Information Exchange Using the Simple Object Access Protocol (SOAP) 135

Introduction 136The Case for Web Services 136

Malformed SOAP Request 163Wrong Argument Types 165Exceptions in Server Code 165Writing a SOAP Client Application 167

Passing Relational Data (DataSets) 179

Showing All Files

through the Solution

Explorer

Passing XML Documents 182

Advanced Web Services 187Maintaining State 187State Information in the URL

(URL Mangling) 189State Information in the Http

Header (Cookies) 191State Information in the Http

Body (SOAP Header) 194Security 202Summary 204Solutions Fast Track 205Frequently Asked Questions 207

Introduction 210Web Service Standards 211Describing Web Services—WSDL 211Discovering Web Services—DISCO 217Publishing Web Services—UDDI 219Working with UDDI 220Summary 228Solutions Fast Track 229Frequently Asked Questions 231

Chapter 6 Building an ASP.NET/ADO.NET Shopping Cart with Web Services 233

Introduction 234Setting Up the Database 234

Setting Up the Table Books 237

Setting Up the Table Categories 237

Setting Up the Table Customer 237

Setting Up the Table Orders 238

Setting Up the Table BookOrders 238

Creating an Access Database 238SQL Server Database 242Creating the Stored Procedures 244

Web Services

Web Services are different from previous technolo- gies used to create distrib- uted systems, such as COM/DCOM, in that:

■ They use open standards.

■ They were designed from the ground up to work on the Internet, including working well with corporate firewalls.

■ They use a “simple”

protocol not requiring multiple round trips to the server.

■ They purposefully don’t address advanced features such as security or transaction support as part of the protocol specification.

Creating the Web Services 250Overview of the Book Shop Web Services 250Creating the Data Connection 252Creating a Web Service 253Testing a Web Service in ASP.NET 259Using WSDL Web References 263

Site Administration 266Creating the Administration Login

(adminLogin.aspx) 266Creating the Administrator

Page (adminPage.aspx) 268Retrieving the Data: Creating the

getBooks.AllBooks Web Method 268Displaying the Data: Binding

a DataGrid to the DataSet 272Adding New Books to the Database:

Creating the allBooks.addItem

Deleting Books: Deleting from

the DataGrid and the Database 272Updating Book Details: Updating

the DataGrid and the Database 273Creating the addBook Page (addBook.aspx) 274Customer Administration 275Creating the Customer Admin Section 275

Creating the loginCustomer Page 275 Creating the updateCustomerInfo Page 276

catalogRange, and catalogByCategory

Methods 281

Answers to Your

Frequently Asked

Questions

Q: My project has a few

different pages in it.

Unfortunately, the last

page I created is the

one that is loaded

when I run the project.

How do I set the first

page to open when I

run the project?

A: In your Project

Explorer, right-click

the file you want and

set it as the Start

Page.

Q: I am working with the

XmlDocument object in

my code-behind page,

and I am not getting

any IntelliSense What

am I doing wrong?

A: Make sure you have

included “Using

System.Xml” in the top

section of the page.

Creating the catalogRangeByCategory

Method 282Building an XMLCart 284Creating the User Interface 287Creating the start.aspx Page 288Rendering the Catalog 289Rendering the Cart 290Creating the Code 290Summary 293Solutions Fast Track 293Frequently Asked Questions 297

Chapter 7 Building a SQLXML

Introduction 300SQLXML Web Services 301Developing the TimeTrack Application 301Creating the Database 302Creating the Stored Procedures 303Creating a SQL Server Virtual Directory 305Enabling Stored Procedures for Soap 310Creating a Client Application in ASP.NET 313Consuming the Web Services 317Summary 333Solutions Fast Track 334Frequently Asked Questions 335

Chapter 8 Building a Jokes Web Service 337

Introduction 338Motivation and Requirements for the Jokes

Functional Application Design 340Defining Public Methods 340Defining the Database Schema 341Defining the Web Service Architecture 342Security Considerations 344State Management 345

Configuring &

Implementing…

SQL Template Queries

Previously accessing SQL Templates server-side from within an ASP.NET

application would fail to load the XML because the security context of the user would be lost when hopping from IIS to SQL.

SQLXML 3.0 solves this problem by allowing server-side access to Template queries by

setting SqlXmlCommand

.CommandType = SqlXmlCommandType TemplateFile.

Error Handling 345Implementing the Jokes Data Repository 345Installing the Database 346Creating the Stored Procedures 348Implementing the Jokes Middle Tier 361Setting Up the Visual Studio Project 361Developing the Error Handler 366Developing the Database Access Component 369Developing the User Administration Service 371Adding New Users 371Checking Existing User Information 376Adding Moderators 379Creating the Public Web Methods—Users 381Error Handling for the Public Web

Methods 384Creating The Public Web Methods—

Administrators 386Testing the Public Web Methods 389Developing the Jokes Service 390Best Practices for Returning Highly

Structured Data 390Setting Up Internal Methods to

Wrap the Stored Procedure Calls 393Setting Up Internal Methods

to Manage Jokes and Ratings 399Setting Up Internal Methods to

Creating the Public Web Methods 413Creating a Client Application 423Some Ideas to Improve the Jokes

Summary 440Solutions Fast Track 441Frequently Asked Questions 443

Error Handling for the

Public Web Methods

The throwFault method

throws a SOAP fault and

ends execution of the Web

Service method But it

does a whole lot more:

■ The (internal) error

custom element, called

failReason, where client

applications can find

the error message to

display to users.

Since it’s inception in February of 1998, XML has been moving forward through thecontinued efforts of the World Wide Web Consortium (W3C) At first many devel-opers scoffed at XML, thinking it was just a new way to script However, thosedevelopers, who regularly worked with database management and development soonrealized that XML could be a way to provide data between parties without needing

to rely on proprietary solutions

At first, this handful of developers began to incorporate snippets of XML intotheir desktop applications to store configuration data or as an export file As timepassed, developers began to apply XML to the Internet Databases began to commu-nicate to each other via XML, and companies were discovering that they had aneasier time coping with external database data thanks to XML

Developers, however, were not the only ones that noticed the possibilities ofXML Microsoft realized the potential of XML, and made it one of the cornerstones

of the NET Framework .NET aims to bridge the gap between desktop applicationsand online applications, and facilitate the communication of objects between the two

At the same time, the concept of Web Services was being developed.

Broadly speaking, a Web Service is the exposure of a business process over a work.The connotation is generally that XML-based traffic is being moved on apublic network (the Internet) via the HTTP protocol However,Web Services canalso be internally useful to an organization, as a mechanism for encapsulating andexposing the business logic inherent in legacy systems New applications can thenutilize this Web Service interface to leverage the complex business logic that has beenrefined, sometimes for decades, in these legacy systems.This allows for the reuse ofsystems at the logical level, without regard to physical configuration

net-Web Services are a fundamental part of the new NET Framework.You can

group Web Services into two categories: producers and consumers A producer Web

Service is one that will retrieve a result set, for instance orders from an e-commerce

xvii

Foreword

database, or Jokes; as in Chapter 8 “Building a Jokes Web Service” A consumer WebService is one that will use that result set of data and do something with it, as in theshopping cart example in Chapter 6 “Building an ASP.NET/ADO.NET ShoppingCart with Web Services.” In this book we will examine both and provide examples ofeach.This book focuses on all aspects of Web Services including: XML, SOAP,

WSDL, UDDI, and the NET Framework

However,Web Services are not limited to just the NET framework and

Microsoft IBM, SUN, and Oracle will all be players in this fast changing ment.The W3C is still working on revisions for SOAP and XML, which means thatthis subject matter is continuously evolving

environ-Taking this a step further, databases will be leveraging their objects as Web

Services, as shown in Chapter 7 “Building a SQLXML Web Service.”This is a

growing segment of Web Services and XML Using the universal versatility of XML,

an application can transport data across multiple platforms and achieve the sameresults Encapsulating this logic in Web Services adds functionality to both the appli-cation and the database

This book assumes that you have prior experience with XML.The code tained in the examples will be in both C# and VB.NET.We will also take a look atSQLXML Web Services along with ADO.NET.You do not have to be a guru to buythis book, but you should possess object oriented programming knowledge to get themost benefit from the code examples If you have any experience in programming atall you should be able to pick up the content easily If you need a more fundamental

con-start, I suggest picking one of these two books, VB.NET Developer’s Guide (ISBN: 1-928994-48-2) and the C# Web Developer’s Guide (ISBN: 1-928994-50-4) Both of

these books offer the proper foundation to properly leverage the knowledge and

information in Developing NET Web Services with XML.

—David Jorgensen, MCP

www.syngress.com

The Syngress Solutions Web site (www.syngress.com/solutions) contains the codefiles, applications, sample databases, and Web Services that are used throughout

Developing NET Web Services with XML.

The code files are located in a chXX directory For example, the files for Chapter

3 are located in folder ch03 Any further directory structure depends upon the WebServices and applications that are presented within the chapter Some of the notablepieces of code include those found in Chapters 6 through 8

In Chapter 6, “Building an ASP.NET/ADO.NET Shopping Cart with WebServices,” readers will find all of the code needed to create a fully functional applica-tion for an online bookseller, that is capable of authenticating users and querying adatabase of both customers and products

Chapter 7, “Building a SQLXML Web Service Application,” includes all of thecode used to create a Web Service for the purpose of project management called

“TimeTracker.”

Finally, Chapter 8, “Building a Jokes Web Service,” includes all of the codeneeded to create a Web Service for interaction between a database of clients, andcontent Code for the GUI is included as well

Look for this icon to locate the code files that will be included on our Web site.

About the Web Site

What Are Web Services?

Solutions in this chapter:

■ Understanding Web Services

■ Using XML in Web Services

■ An Overview of the System.Web.Services Namespace

; Solutions Fast Track

; Frequently Asked Questions

Web Services provide a new level of interaction to all kinds of applications.Theability to access and use a remote Web service to perform a function within anapplication enables programmers to quickly deliver a more sophisticated applica-tions in less time.The programmer no longer has to create and maintain all func-tions of the application Reusability is also greatly enhanced by creating multipleWeb services that perform functions in multiple applications, thus freeing up timeand resources to work on other aspects of specific projects See Figure 1.1, whichshows a graphical representation of this process

www.syngress.com

Figure 1.1Where Do Web Services Fit In?

Host Web Services

Internet and Database Servers

Data

Host Web Pages

Internet Servers IIS

Host Web Pages Host Web Pages

In this chapter we will be looking at a simple Hello World Web Service ered via ASP NET.This Web Service example can be accessed by any applicationthat can handle Simple Object Access Protocol (SOAP).

deliv-Web Services function primarily through XML in order to pass informationback and forth through the Hypertext Transfer Protocol (HTTP).Web Servicesare a vital part of what the NET Framework offers to programmers XML-baseddata transfer is realized, enabling primitive types, enumerations, and even classes to

be passed through Web Services to the application performing the request.Thisbrings a whole new level of reusability to an application XML is the backbonefrom which the whole Framework is built.The user interface (UI) can be created

by applying Extensible Stylesheet Language Transformations (XSLTs) or by

loading the data into DataSets and binding to Web Controls Having XML as the

intermediary enables new avenues of client design

Understanding Web Services

Web Services are objects and methods that can be invoked from any client overHTTP.Web Services are built on the Simple Object Access Protocol (SOAP)

Unlike the Distributed Component Object Model (DCOM) and Common ObjectRequest Broker Architecture (CORBA), SOAP enables messaging over HTTP onport 80 (for most Web servers) and uses a standard means of describing data SOAPmakes it possible to send data and structure easily over the Web.Web Services capi-talizes on this protocol to implement object and method messaging.Web Services

are easy to create in VS.NET Here is an ASP.NET Hello World class in C#:

public class hello {

public string HelloWorld() {

return "Hello World";

} } }

This class describes a hello object that has one method, HelloWorld.When called, this method will return data of type string.To convert this to a Web Service

method, we simply have to add one line of code:

public class hello {

A little bit more code is involved to make this a method of a Web Service.This is the code that VS.NET auto-generates when we create a new asmx page,

along with our Hello World method:

InitializeComponent();

} private void InitializeComponent() {

} protected override void Dispose( bool disposing ) {

} [WebMethod]

public string HelloWorld() {

return "Hello World";

}

www.syngress.com

} }

You can quickly create this class in VS.NET by creating and opening a C#

Web Application project or Web Service project and adding a new WebServicepage

If you prefer, similar code could be written to create a VB.NET Service:

Imports System.Web.Services

Public Class Service1 Inherits System.Web.Services.WebService

<WebMethod()> Public Function HelloWorld() As String

HelloWorld = "Hello World"

End Function

End Class

To run this sample in VS.NET, simply press F5 It will take a few moments to

build and compile.When that phase is complete, you should see the Hello servicescreen shown in Figure 1.2

The top line on the screen states that the operations listed below it are ported.This is followed by a bulleted list of links to each of the Web methodsthat belong to the Web service In our case, we created only one Web method,

sup-HelloWorld If you click the link HelloWorld, you will be taken to that service’s

description page (see Figure 1.3)

Setting the Start Page

When testing a Web service in a project that contains other aspx or asmx files, be sure to set the file you are debugging/testing to be the Start page, before running To do this, right-click the filename in the

Solution Explorer and select Set as start page.

Debugging…

Figure 1.2Hello Service

Figure 1.3HelloWorld Service Description Page

To test our Hello Web Services HelloWorld Web method, simply click the

Invoke button and our method will be called Recalling our method returns thestring “hello world”; the result is returned in an XML wrapper (see Figure 1.4)

Note that the XML node reflects the datatype of the method’s return value,

string.This XML message is received and converted to the string “Hello World”.

This means that any variable (of type string) in our code can be assigned to the

result of our Web method

Figure 1.4Results from Invoking the HelloWorld Web Method

Building and Compiling

If you have experience programming in C/C++ or Java, you will be familiar with the building and compiling steps If you are a Web Developer who hasn’t really played with a compiled language before, these steps will be new to you Think of it as the phase in which the com- piler gets all your code together and checks it for unassigned variables, variable type mismatches, and other syntactic errors In this phase, it also converts your code into the Common Language Runtimes (CLR) Intermediate Language (IL), and then into machine language This will allow the code to run faster and more efficiently than uncompiled script.

After this phase completes, the code is run in the Browser So, testing Web page output may seem to take longer in the NET environment.

Developing & Deploying…

Communication between Servers

The concept of sending messages between servers or remotely calling functions isnot new.Technologies such as DCOM and CORBA are well-known proprietaryprotocols that have been in use for years.What is new is the use of a standardprotocol to transfer messages over HTTP, that protocol is SOAP SOAP makes itpossible for applications written in different languages running on different plat-forms to make remote procedure calls (RPC) effectively, even through firewalls.DCOM doesn’t use port 80, which is reserved for HTTP traffic; this causesDCOM calls to be blocked by firewalls SOAP calls use port 80, which makes itpossible to call procedures that exist behind firewalls Figure 1.5 shows a highlevel overview of how Web Services can be used, both for customer interactionswith a company from multiple client types as well as for internal company datagathering and reporting between all company servers, including legacy systems

Server Data

Branch Office

Server Data

Customers

Corporate / Customer Web Services

Corporate Reporting Web Services

Investment Brokerage House

Customer Web Services Branch kiosk can allow customers to pull or retrieve account information.

Corporate Website can allow customers to pull or retrieve account information.

Corporate Web Services Branch offices can push reporting data to corporate servers.

Corporate can pull branch reporting data.

Soap / HTTP Using SOAP over HTTP enables servers running different operating systems to communicate seamlessly over the Internet.

Soap / HTTP Using SOAP over HTTP enables applications written in different languages to communicate seamlessly over the Internet.

In ASP.NET,Web Services and their methods are defined in pages with the.asmx extension.When we create Web Services, the NET Framework generates aWeb Services Description Language (WSDL) file on the server hosting theService; this WSDL file describes the Web Service interface On the Web server

that hosts our aspx pages,VS.NET generates a WSDL proxy when we click Add

Web reference in the Solutions Explorer and select the server and Service

Customers

WSDL Server Data

Scenario Web user makes an online purchase:

• One method call could verify and process the credit card with a Web Service supplied by the credit card organization.

• Another method could contact a Web service supplied by the shipping company to calculate shipping charges.

• Another Web service from within the organization could remove the item from active inventory and flag it for shipping.

A single application hosted on the Web server may access several Web Services residing on different servers Likewise, many Web servers may access one Web Service.

.asmx Files

ASP.NET uses the asmx file extension for defining ASP.NET Web Services.Thecode-behind pages are asmx.cs and asmx.vb for C# and VB.NET, respectively

www.syngress.com

Figure 1.7Web References in VS.NET’s Solution Explorer Window

What Is the Difference between asmx and aspx?

In ASP, we have the asp extension to denote an Active Server Page When IIS sees this extension, it knows it has some extra processing to

do This is the same with ASP.NET, except that we have two new sions, aspx and asmx.

exten-Migrating…

Continued

While the client for an aspx page is the Web browser, the client for an asmxfile is the Web server Since they are used as programming interfaces and notdirectly utilized by the Web user, asmx files should not contain any UI.To get abetter understanding of how this all works, lets create an aspx page that calls our

“Hello” service

1 In the Solutions Explorer, right-click the project name.

2 Select Add | New Item.

3 Select Web Form Name the file helloPage.aspx.

4 While in design view, open the toolbox and drag onto the page a labeland a button control from the selection of Web Forms (see Figure 1.8)

While still in design mode double-click the new button.This willgenerate event code in the code behind page (see Figure 1.9)

5 Right-click References in the Solution Explorer and select Add

Web Reference.This is basically a graphical user interface (GUI) forthe WSDL.exe command line utility

Lets do a quick comparison:

■ Both file types have a template, which includes references to the primary namespaces.

■ aspx pages have references to System.Drawing since their purpose is to generate a user interface.

■ asmx pages have references to System.Web.Services since their purpose is to generate an interface for external pro- grams.

■ You can add UI components and DataConnections to an aspx page.

■ You can add Server and DataConnections to an asmx page.

■ aspx pages usually begin with an @Page directive to nate: this is a WebForm.

desig-■ asmx pages usually begin with an @WebService directive to designate: this is a Web Service.

■ Using the wrong @ directive with the wrong type of file extension will generate an error.

Figure 1.8Adding a Web Form Control to an aspx Page

Figure 1.9Auto-generated Button Event Code

6 When the Add Web Reference dialog opens (see Figure 1.10) click the link Web References on local server.

The dialog will pause while it searches your local machine for a list

of services available

7 When the list appears, click the name of the service that matches the

name of your project, WebApplication_HelloWorld.

8 When the service loads, click the Add Reference button.This will

create several new entries in your Solutions Explorer

9 Now take a look at helloPage.aspx in HTML view.You should see codesimilar to the following:

<body MS_POSITIONING="GridLayout">

<form id="helloPage" method="post" runat="server">

<asp:Button id=Button1 Text="Button" runat="server" >

10 Note the name of the label control is Label1 Now open

helloPage.aspx.csand add the following code below the label andbutton code

localhost.hello test = new localhost.hello();

11 In the Button Click handler, add the following:

Label1.Text = test.HelloWorld();

12 Your code should now look like Figure 1.11

13 Right-click helloPage.aspx and click Set as start page.

14 Press F5 to run the application.

15 When the browser loads, click the button, this will invoke our helloWorld

method and assign its value to the label text After clicking the button,your page should look like Figure 1.12

www.syngress.com

Figure 1.11helloPage.aspx.cs

WSDL is an XML-based language that describes Web Services It is the posite of work done by Ariba, IBM, and Microsoft Currently, it only supportsSOAP as a messaging protocol

com-The thought behind WSDL is that in future applications it will be a tion of networked-Web Services.WSDL describes what a service can do, where itlives, and how to invoke it.WSDL describes the Web Service method interfacesthoroughly enough for it to be used to create proxy methods that enable otherclasses to invoke its members as if they were local methods IBM and Microsoftboth have WSDL command line utilities available that do just that IBM does itfor Java, and Microsoft does it for Visual Studio.VS.NET has this ability built into

collec-the GUI In VS.NET, we simply right-click add Web Reference and select collec-the

service we want to generate a proxy class for Here is an example of a WSDL filefor a Web Service: getCategories.wsdl.This file is auto-generated by the NETFramework

While the auto-generated file will cover the basic functionality, it may domore or less than you intended.The auto-generated code can be simplified byremoving support for asynchronous operations if you do not need to support thistype of operation Also, you could add custom SOAP headers and customizeother parts of the SOAP envelope by creating your own class WSDL and UDDIare covered in later chapters

Figure 1.12HelloPage.aspx in the Browser after Clicking the Button

Using XML in Web Services

Web Services use SOAP as a messaging protocol SOAP is a relatively simpleXML language that describes the data to be transmitted.Why use XML? XML

is a standard language designed to be understandable by humans, and structured

so it can be interpreted programmatically XML does not only describe data, itcan also describe structure, as we will see when we take a closer look at the

ADO.NET DataSet.

Consider the case of replicating a database into cache.We might want to dothis to reduce the load on the database server, to speed client processing, or toprovide an offline data handling scenario.We could transport an XML documentthat contains the new W3C XML Schema Definition Standard (XSD) schemadescribing the database tables, relations, and constraints, along with the actual data(see the section “Using DataSets” later in this chapter) Because XSD can

describe relational data and can be embedded within an XML document, anydatabase can be converted to a ubiquitous data source.That is, a data source thatcan be accessed on any platform by any application.This is possible because thetransfer protocol, SOAP, uses XML over HTTP and because XML, XSD, SOAP,and HTTP are all nonproprietary industry standards

It is the use of non proprietary industry standards that makes Web Services sopowerful By using XML to describe structure and content,Web Services canprovide an interface to data on legacy systems, or between incompatible platformsfrom acquisitions or between vendors over intranets, extranets, or the Internet

An Overview of the System.Web.Services Namespace

System.Web.Services is the namespace from which all Web service classes are

derived It consists of all the classes needed to create Web Services in the NET

Framework.When using VS.NET most of the System.Web.Services classes and

sub-classes are transparent to the developer, so we won’t go into much depth here

The three primary child classes of System.Web.Services are: Description, Discovery,

and Protocols

The System.Web.Services.Description Namespace

The System.Web.Services.Description namespace contains the classes needed to

describe a Web Service using the Microsoft SDL (Service Definition Language), aMicrosoft implementation of the WSDL standard.VS.NET uses these classes tocreate the disco or vsdisco file Many of the subclasses of this class are related tobinding: MessageBinding, OperationBinding, OutputBinding, and so on One of

the more interesting subclasses is the ServiceDescription class It takes as a parameter

an XML file and enables the creation of a valid WSDL file

ServiceDescription MyDescription = new ServiceDescription();

ServiceDescription MyDescription =

ServiceDescription.Read("MyTestFile.xml");

The System.Web.Services.Discovery Namespace

The System.Web.Services.Discovery namespace consists of the classes that enable

Web Service consumers to locate available Web Services In VS.NET when wecreate a Web Reference, these classes find the vsdisco files that describe WebServices

Disco file from our Hello World example:

docRef="http://localhost/WebApplication_HelloWorld/hello.asmx"

xmlns="http://schemas.xmlsoap.org/disco/scl/" />

</discovery>

The System.Web.Services.Protocols Namespace

The System.Web.Services.Protocols namespace consists of the classes used to define

the protocols that enable message transmission over HTTP between ASP.NETWeb Services and ASP.NET Web Service clients.These classes are used in ourWSDL proxy classes.They are mostly involved with the formatting, bindings, andsettings of the SOAP message

WSDL proxy from our Hello World example:

"http://localhost/WebApplication_HelloWorld/hello.asmx"; }

[System.Diagnostics.DebuggerStepThroughAttribute()]

[System.Web.Services.Protocols.SoapDocumentMethodAttribute(

"http://tempuri.org/HelloWorld", Use=System.Web.Services.Description.SoapBindingUse.Literal, ParameterStyle=

System.Web.Services.Protocols.SoapParameterStyle.Wrapped)] public string HelloWorld() {

object[] results = this.Invoke("HelloWorld", new object[0]);

www.syngress.com

return ((string)(results[0]));

}

[System.Diagnostics.DebuggerStepThroughAttribute()]

public System.IAsyncResult BeginHelloWorld(

System.AsyncCallback callback, object asyncState) {

Type Marshalling

Type marshalling refers to the translation of datatypes from an application or

database as it is mapped to a SOAP datatype.When any datatype, object, method,

or string (xml, or a simple string) is passed as a SOAP request or response, it isautomatically converted into an XML representation of itself Since any program-ming language can use SOAP, SOAP has defined its own set of datatypes.Whendata is passed in a SOAP envelope its datatypes are translated or converted to aSOAP equivalent.This enables different languages with different names for similardatatypes to communicate effectively.The datatypes supported when using WebServices include:

■ Standard primitive types String, char, Boolean, byte, single, double, DateTime, int16, int32, int 64, Uint16, and so on.

string "hello World" is represented as:

<string>hello World</string>