The document discusses creating and using web services. It describes web services as reusable code that exposes methods to be called by other applications regardless of programming language or platform. The key technologies that enable web services are XML, SOAP, WSDL and UDDI. The document provides steps for creating a web service, including defining methods, creating a project, and accessing the web service from a client application. It also discusses using web services in both local and web-based applications.

1. Creating and Using Web Services
Objectives
In this lesson, you will learn to:
Identify the need for Web services
Identify the enabling technologies in Web services
Create a Web service
Use a Web service in a Visual Basic .NET local application
Use a Web service in a Web application
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2. Creating and Using Web Services
Web Service
Is similar to a component that provides a specific
functionality.
Exposes a number of methods that provide functionality that
can be used by one or more applications, regardless of the
programming languages, operating systems, and hardware
platforms used to develop them.
Functionality can be accessed by applications by using
Internet standards, such as HTTP and XML.
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3. Creating and Using Web Services
Web Service (Contd.)
Can be of different types:
One that provides a fundamental functionality, which
can be used in multiple applications.
Second that can integrate the existing applications that
might have been created using different software and
hardware platforms.
Third that can be a means to exchange data in
business-to-business transactions.
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4. Creating and Using Web Services
Enabling Technologies Used in Web Services
A Web service can be developed by using any
programming language in .NET suite. However, it requires:
A common data representation format in order to ensure
the interoperability of the data exchanged by the client
application and the Web service.
A standard method for sending messages from the
client application to the Web service and vice versa.
A standard format for describing the Web service.
A mechanism to allow client applications to discover the
Web services and their locations.
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5. Creating and Using Web Services
Enabling Technologies Used in Web Services
(Contd.)
Requirements are fulfilled by using various standards
such as:
eXtensible Markup Language (XML) - Allows data
interchange regardless of the hardware and software
platform used to develop the application.
Simple Object Access Protocol (SOAP) - Is a standard
communication protocol for interchanging information in
a structured format in a distributed environment.
Web Services Description Language (WSDL) – Is an
XML vocabulary that describes the methods that are
exposed by a Web service.
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6. Creating and Using Web Services
Enabling Technologies Used in Web Services
(Contd.)
Universal Description Discovery and Integration (UDDI)
- Is used as a standard mechanism to register and
discover a Web service provided by various Web
service providers.
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7. Creating and Using Web Services
Just a Minute…
What is the difference between a Web service and a
component?
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8. Creating and Using Web Services
Problem Statement 15.D.1
The Call Center application needs to provide a facility for
various departments to view the status of the queries received
from various customers. The organization also plans to
provide a facility to its customers to find out the status of their
queries through a Web site. For this, a reusable code needs to
be written so that both local and Web applications can access
the details about queries.
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9. Creating and Using Web Services
Task List
Identify a mechanism for writing reusable code.
Identify the methods to be exposed to applications.
Create a Web service project.
Create the methods to be exposed to applications.
Execute the application.
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10. Creating and Using Web Services
Task 1: Identify a mechanism for writing reusable
code.
Result:
A Web service allows applications to transfer data by using
standard protocols and data formats. Therefore, in the given
scenario, you can create a Web service that exposes a
Web method to access query details.
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11. Creating and Using Web Services
Task 2: Identify the methods to be exposed to
applications.
Result:
In the given scenario, you need to create a Web service and
expose a Web method that takes a query ID as a
parameter. The Web method should retrieve the details
about the query and populate a DataSet object with the
query details. This DataSet object should be returned to the
client application that uses the Web service.
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12. Creating and Using Web Services
Task 3: Create a Web service project.
Task 4: Create the methods to be exposed to
applications.
Code model for Web services
A Web service is composed of two parts, the Web
service entry point and the code that provides the
functionality to be used by other applications.
The .asmx file serves as the entry point for the Web
service.
The .asmx file accesses the code from precompiled
assemblies and the code-behind (.vb) file
corresponding to the Web service.
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13. Creating and Using Web Services
The code-behind file imports the
System.Web.Services namespace, which contains
the classes that are required to build and use Web
services.
All Web service classes inherit the WebService class,
which belongs to the System.Web.Services
namespace.
While writing code within the Web service class, you
can use the following attributes:
® WebService:Used to provide additional information
about the Web methods exposed by a Web service.
® WebMethod: Used for every method that needs to
be exposed for use by other applications.
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14. Creating and Using Web Services
Task 5: Execute the application.
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15. Creating and Using Web Services
Problem Statement 15.D.2
A form needs to be designed in the Call Center application to
display the details about a query. The code for retrieving the
details about a query is provided in the GetQueryData Web
service. This Web service needs to be used in the Call Center
application to enable various departments of Diaz
Telecommunications to view the status of queries.
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16. Creating and Using Web Services
Task List
Identify the data to be displayed.
Design the user interface.
Write the code to display data by using the functionality
exposed by the Web service.
Execute the application.
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17. Creating and Using Web Services
Task 1: Identify the data to be displayed.
Result:
The data to be displayed includes:
Query ID
Date of submission
Customer ID
Employee ID
Response date
Status
Feedback
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18. Creating and Using Web Services
Task 2: Design the user interface.
Task 3: Write the code to display data by using the
functionality exposed by the Web service.
To access the functionality exposed by a Web service,
perform the following tasks:
Locate the Web service that provides the functionality
required in the application.
Create a proxy class for the Web service.
Reference the proxy class in the application code.
Instantiate the proxy class.
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19. Creating and Using Web Services
Task 4: Execute the application.
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20. Creating and Using Web Services
Just a Minute…
2. How can you locate the Web services developed by a Web
service provider?
3. Which attribute is used to describe a Web service?
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21. Creating and Using Web Services
ASP.NET
Is a powerful programming framework for the development
of enterprise-class Web applications.
Is a part of the .NET Framework.
Provides access to all the features of the .NET Framework.
Therefore, you can develop an ASP.NET Web application
by using any of the programming languages provided in
.NET, such as Visual Basic .NET and C#.
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22. Creating and Using Web Services
Elements of ASP.NET
User interface - For accepting input and displaying text to a
user in an ASP.NET Web application, Web Forms are used.
The working of a Web Form is similar to that of a Windows
Form except that the user interface is typically rendered in a
Web browser.
Components – For providing reusable code and adding
business logic in an ASP.NET Web application, Web
services are used.
Data - For accessing data stored in a database in an
ASP.NET Web application, ADO.NET is used.
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23. Creating and Using Web Services
Web Form
Allows you to create programmable Web pages that serve
as a user interface for your Web application.
Provides a combination of HTML, various Web Form
controls, and code. Code provided in a Web Form is
executed on a Web server running Internet Information
Services (IIS) 5.0.
Can be used to interact with any Web application regardless
of the browser or the type of computer used by them.
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24. Creating and Using Web Services
Summary
In this lesson, you learned that:
A Web service exposes functionality that can be used by
one or more applications, regardless of the
programming languages, operating systems, and hardware
platforms used to develop them.
The functionality exposed by a Web service can be
accessed by applications by using Internet standards, such
as HyperText Transfer Protocol (HTTP) and eXtensible
Markup Language (XML).
A Web service can be created using any programming
language in .NET suite, such as Visual Basic .NET, Visual
C#.NET, and Visual C++.NET.
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25. Creating and Using Web Services
Summary (Contd.)
Web services use eXtensible Markup Language for
interchanging data in a standard format between different
applications.
To be able to communicate with each other, a Web service
and a client application must agree upon a common
protocol. SOAP is a standard communications protocol
for interchanging information in a structured format in a
distributed environment.
To be able to use a Web service, the developers of a client
application need to know the methods exposed by the
Web service and the parameters to be passed to these
methods. Web Services Description Language (WSDL) is
a markup language, which is used to describe a Web
service.
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26. Creating and Using Web Services
Summary (Contd.)
The Universal Description Discovery and Integration (UDDI)
initiative is used to allow client applications to discover
the Web services provided by various Web service
providers.
A Web service consists of two parts, the Web service entry
point and the code that provides the functionality that
is used by other applications.
The .asmx file serves as the entry point for the Web service.
The WebService attribute is an optional attribute that can
be used to provide additional information about the
Web methods exposed by a Web service.
You must place the WebMethod attribute before the
declaration of every method that needs to be exposed for
use by other applications.
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27. Creating and Using Web Services
Summary (Contd.)
In order to be able to access the functionality exposed by a
Web service, you need to perform the following tasks:
Locate the Web service that provides the functionality
required in the application.
Create a proxy class for the Web service.
Reference the proxy class in the application code.
Instantiate the proxy class.
Visual Studio .NET provides you with an integrated
development environment for creating Web applications
ranging from traditional Web sites consisting of several
HTML pages to sophisticated business-to-business
applications that provide Web-based components for
performing data interchange between trading partners.
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28. Creating and Using Web Services
Summary (Contd.)
The Web applications developed using Visual Studio.NET
are built on ASP.NET, which is a powerful
programming framework for the development of enterprise-
class Web applications.
ASP.NET is a part of the .NET Framework. It provides
access to all features of the .NET Framework.
An ASP.NET Web application has the same elements as
any other client-server application. These elements are
the user interface, components, and data.
Web services can be effectively used in both local and Web
applications. Using a Web service in an ASP.NET Web
application involves the same steps as in the case of a
Windows application.
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