Topik 5.1 Understand Web Forms

7/30/2019 Topik 5.1 Understand Web Forms

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F5227VISUAL BASIC .NET PROGRAMMING

Topic 5.0:

WEB FORMS AND XML WEB SERVICES


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Course Learning Outcome (CLO) Upon completion of this course, students should be able to :

1. Create a simple VB.NET based application based on the

Windows Application template.

2. Describe on essential terminology including memory,data types and graphical user interface.

3. Apply object oriented programming techniques to

create classes, add methods and add properties.

4. create a simple VB.NET

based Web forms applicationthat uses an XML Web Service and manipulate data in

database by using Microsoft ADO.NET.


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Course Learning Outcome:

Topic 5.0

1. create a simple VB.NET based Web forms application

that uses an XML Web Service and manipulate data in

database by using Microsoft ADO.NET


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Topic 5.0

Topic 5.1 : Understand with Web Forms

Topic 5.2 Create a web application using

VB.NET

Topic 5.3 : Work with Data using ADO.NET


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Topic 5.1

Understand with Web Forms (XML and Web

Services)


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Introduction

Web Forms are based on ASP.NET.

Working with Web Forms is similar to working

with Windows Forms.

But the difference is that we will create Web

pages with Web forms that will be accessible

by a Web browser.


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Web Forms are Web pages that serve as the

user interface for a Web application.

A Web Forms page presents information to

the user in any browser or client device and

implements application logic using server-side

code.


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Web Forms Hierarchy

Web Forms are based on

the System.Web.UI.Page class.

The class hierarchy for the page class is shown

below.

Object

Control

TemplateControl

Page


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Components of Web Forms

In Web Forms pages, the user interface

programming is divided into two parts:

the visual component (design page)

the logic (code behind page).


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The visual element is the Web Forms page.

The page consists of a file with static HTML, or

ASP.NET server controls, or both

simultaneously.

The Web Forms page works as a container for

the static text and the controls we want to

display.


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Using the Visual Studio Web Forms Designer

and ASP.NET server controls, we can design

the form just like in any Visual Studio

application.


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The Files

The logic for the Web Forms page consists of

code that we create to interact with the form.

The programming logic is in a separate file

from the user interface file.

This file is the "code-behind" file and has an

".aspx.vb" (VB) or ".aspx.cs" (C-Sharp)

extension.

The logic we write in the code-behind file can

be written in Visual Basic or Visual C#.


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The code-behind class files for all Web Forms

pages in a project are compiled into the

project dynamic-link library (.dll) file.

The .aspx page file is also compiled, but

differently.

The first time a user loads the aspx page,

ASP.NET automatically generates a .NET class

file that represents the page, and compiles it

to a second .dll file.


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The generated class for the aspx page inherits

from the code-behind class that was compiled

into the project .dll file.

When the user requests the Web page URL,

the .dll files run on the server and dynamically

produces the HTML output for your page.


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Web Forms


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.aspx file

The form opens in design mode and you can

switch to HTML view by clicking on the HTML

tab.

Startvbdotnet.aspx file in the image is

standard HTML with ASP elements embedded

in it


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.aspx file

The codebehind attributeconnects this code to the

appropriate Visual Basic or

C# code (code behind file)


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Code BehindPublic Class Startvbdotnet Inherits System.Web.UI.Page

Protected WithEvents TextBox1 As System.Web.UI.WebControls.TextBox

Protected WithEvents Button1 As System.Web.UI.WebControls.Button

Protected WithEvents Label1 As System.Web.UI.WebControls.Label

#Region " Web Form Designer Generated Code "

'This call is required by the Web Form Designer.

Private Sub InitializeComponent()

End Sub

Private Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs)_

Handles MyBase.Init

'CODEGEN: This method call is required by the Web Form Designer

'Do not modify it using the code editor.

InitializeComponent()

End Sub

#End Region

Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs)_

Handles MyBase.Load

'Put user code to initialize the page here

End Sub

End Class


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The ASPX Extension

Many of us wonder why the extension for

ASP.NET is .aspx.

Well, long time ago, when ASP.NET was being

developed at Microsoft it was referred to as

ASP+ (ASP Plus).


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You can't use a "+" symbol in a filename but if

you turn the + symbol about 45 degrees, it

looks like a x. Microsoft chose .aspx as the

extension of ASP+.

After the name was changed to ASP.NET,

Microsoft did'nt change the extension and left

it as aspx.


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What is Web Service

The term "web service" refers to a form of a

component that can be used remotely.

Microsoft offers two types of web services in

their .NET framework:

XML web services

.NET remoting.

When developers refer to web services they

usually mean XML web services
http://www.developerfusion.com/t/.net/http://www.developerfusion.com/t/xml/http://www.developerfusion.com/t/xml/http://www.developerfusion.com/t/.net/


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Web Service


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XML Web Services

Web services are invoked remotely using

SOAP or HTTP-GET and HTTP-POST protocols.

Web services are based on XML and return an

"answer" to the client in XML format.

Web services have all the advantages of

components plus many more.


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Advantages of XML Web Services

Language and platform independence:

Web services can be built and consumed on

any operating system just as long as that

operating system supports the SOAP protocol

and XML.


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XML

XML files are plain text files just like HTML

files.

XML can easily be stored and generated by a

standard web server.


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Generating XML with ASP

XML can be generated on a server without any

installed XML software.

To generate an XML response from the server

- simply write the following code and save it as

an ASP file on the web server:


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XML in ASP

Note that the content type of the response

must be set to "text/xml".


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Web Services

Web Services can convert your application

into a Web-application, which can publish its

function or message to the rest of the world.

The basic Web Services platform is XML +

HTTP.


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What are Web Services

Web services are application components

Web services communicate using open

protocols

Web services are self-contained and self-

describing

Web services can be discovered using UDDI

Web services can be used by other

applications

XML is the basis for Web services


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How Does it Work?

The basic Web services platform is XML +

HTTP.

XML provides a language which can be used

between different platforms and programming

languages and still express complex messages

and functions.

The HTTP protocol is the most used Internet

protocol.


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Elements

Web services platform elements:

SOAP (Simple Object Access Protocol)

UDDI (Universal Description, Discovery and

Integration)

WSDL (Web Services Description Language)


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How its works?


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What is SOAP

SOAP is an XML-based protocol to let

applications exchange information over HTTP.

Or more simple: SOAP is a protocol for

accessing a Web Service.


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About SOAP

SOAP stands for Simple Object Access Protocol

SOAP is a communication protocol

SOAP is a format for sending messages

SOAP is designed to communicate via Internet SOAP is platform independent

SOAP is language independent

SOAP is based on XML

SOAP is simple and extensible SOAP allows you to get around firewalls

SOAP is a W3C standard


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What is WSDL?

WSDL is an XML-based language for locating

and describing Web services.

WSDL stands for Web Services Description

Language

WSDL is based on XML

WSDL is used to describe Web services

WSDL is used to locate Web services WSDL is a W3C standard


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What is UDDI?

UDDI is a directory service where companies

can register and search for Web services.

UDDI stands for Universal Description, Discovery and

Integration UDDI is a directory for storing information about web

services

UDDI is a directory of web service interfaces described by

WSDL UDDI communicates via SOAP

UDDI is built into the Microsoft .NET platform


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Advantages

Reusable application-components.

There are things applications need very often

Connect existing software.

Web services can help to solve the interoperability

problem by giving different applications a way to

link their data.

With Web services you can exchange databetween different applications and different

platforms.


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Conclusion

Web service is one of the greatest

technologies in the Internet world; it can be

used to connect businesses with each other

and clients in a standard way using XML(Extensible Markup Language), SOAP (Simple

Object Access Protocol), WSDL (Web Services

Description Language) and UDDI (UniversalDescription, Discovery and Integration).


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Conclusion

XML is used for structuring the data, SOAP is

used to transfer the data, WSDL is used for

describing the services and UDDI is used to get

a list of services available.

Web service allows applications to

communicate with each other without

worrying about hardware systems, operatingsystems and programming languages.

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Topik 5.1 Understand Web Forms