Lecture Learning programming using Visual Basic Net – Chapter 11 Using VISUAL Basic NET to create web applications

After studying this chapter you should be able to Explain the various functions of a typical web application, explain what is meant by the term clientserver and how the clientserver architecture can be implemented in a number of different ways, discuss the tradeoffs associated with various clientserver architecture options,...

Using Visual Basic NET to Create Web Applications

• We will look at applications where various parts

of the application run on the client as well as

• An application is divided into three primary

functions:

– Presentation (GUI).

– Processing business logic.

– Data management.

• We will look at data validation

• We will examine processing databases in the

Web Application context

Introduction (cont.)

• The chapter is ended with a project that

demonstrates how two or more Web pages can

communicate with each other by sharing data

• Explain the various functions of a typical Web

Application

• Explain what is meant by “client/server.”

• Explain how the client/server architecture can be implemented in a number of different ways

• Discuss the trade-offs associated with various

client/server architecture options

Objectives (cont.)

• Build a Web Application using the tools available with Visual Basic NET

• Validate user data using the Validation controls

supported by Visual Basic NET

• Use the Web Form DataGrid control to display a

data set and to edit and update a database

• Use XSLT documents to transform XML into

HTML on the server to then be displayed on the

client

• It is useful to break an application down into

three primary functions:

– Presentation involves how the application

interacts with the user.

– Business Logic involves rules that define how the

application handles data and processes them.

– Data Management involves databases and

software to management these databases

11.1 An Introduction to Functional Web

Architectures (cont.)

• Architecture refers to how these three functions

are allocated to various computers

• Client refers to the computer (or other intelligent

device) that the user is using

• Server refers to another computer that is distinct

from the client and may be located anywhere in

the world

– One server is referred to as two-tier architecture.

– More than two servers are referred to as n-tier

architecture.

Architectures (cont.)

• Presentation

– Option 1: Pure HTML.

• Any changes seen on the browser need to be sent

to the browser from the Web server.

• This option is unacceptable.

– Option 2: Script Within the Browser.

• Script are embedded within the HTML code sent from the server to the browser.

• Creates very powerful user interfaces.

11.1 An Introduction to Functional Web

Architectures (cont.)

• Business Logic

– Option 1: All Client.

• The application runs exclusively on the client computer.

• Low bandwidth requirement.

• For medium and large organizations, problems involve software installation and maintenance.

• Limited use.

Architectures (cont.)

– Option 2: Embed Business Logic in a Web Page

Using Client-Side Scripting.

• Uses scripts that are interpreted in the browser.

• Scripts process business logic.

• Overcomes the installation and maintenance problems of Option 1.

• Problem with user ability to view the scripts.

11.1 An Introduction to Functional Web

• Shares the advantages of Option 2.

• Overcomes the problem of script visibility.

• Requires large bandwidth.

• Security is a major problem.

• Microsoft uses a trusted application model.

Architectures (cont.)

– Option 4: Process Business Logic on the Server.

• Business logic is processed on the server.

• Communication between a Web server and client browser.

• Implemented using Active Server Pages (ASP).

• Includes all the advantages of Option 3 without the disadvantages of potential large bandwidth and

trusted application issues.

11.1 An Introduction to Functional Web

Architectures (cont.)

• Data Management

– Option 1: Client-Side Only.

• Database and database management system are both on the client.

• Speed is the advantage.

• No network issues.

• No issues with multiple users.

• Problems with database consistency, installation, and maintenance.

11.1 An Introduction to Functional Web

Architectures (cont.)

– Option 2: Server-Side Only.

• Database and DBMS are both on the server.

• Problem with communicating requests to the server.

11.1 An Introduction to Functional Web

Architectures (cont.)

• Summary

– Many different options for processing

presentation, business logic, and data

management functions.

– The choice of options is critical to application

success.

• Creating a Simple Web Application

– Visual Basic NET provides a template to create a new Web Application project.

– Use ASP.NET Web Application instead of

Windows Application.

– The extension for the Web form is “.aspx”.

– Complete Example 11.1, Simple Web Application,

11.2 ASP.NET Web Applications (cont.)

• Validating User Input

– Validator controls for Web Forms provide the

means for checking the contents of other

• Validation Controls for Web Forms

Type of Validation Control to Use

Required entry RequiredFieldValidator

Comparison to a value CompareValidator

Range checking RangeValidator

Pattern matching RegularExpressionValidator

User-defined CustomValidator

11.2 ASP.NET Web Applications (cont.)

– Complete Example 11.2, Validating User Input, in

your textbook.

Chapter Summary

• The three primary functions of any application

are presentation, business logic, and data

management

• With Web Applications, presentation is almost

always managed on the client using a browser

• The processing of business logic can be

handled on the client or server

• Processing simple business rules is best done

with embedded script on the client

• Complex and/or proprietary business logic

typically should be done on the server

• Data management is typically handled on a

Chapter Summary (cont.)

• Background HTML code is created automatically

by Visual Basic NET

• Web Forms include a number of Validator

controls that can be added to the project

• Validation is automatically done in the browser

on the client by script

• The DataGrid control for the Web Form supports

the display of datasets

• XML processing is available to the Web Form.

• Visual Basic NET provides methods to maintain

a session within ASP.NET