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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,...
CHAPTER ELEVEN Using Visual Basic NET to Create Web Applications 11- Introduction • We will look at applications where various parts of the application run on the client as well as servers • Visual Basic NET has a powerful set of Web Application tools • This is made possible using Microsoft’s ASP.NET technology • Different Web architectures are examined McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11- Introduction (cont.) • 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11- 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11- Objectives • 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11- 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11.1 An Introduction to Functional Web Architectures 11- • 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11.1 An Introduction to Functional Web Architectures (cont.) 11- • 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11.1 An Introduction to Functional Web Architectures (cont.) 11- • 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 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 ã Limited use McGraw Hill/Irwin â2002 by The McGraw-Hill Companies, Inc All rights reserved 1110 11.1 An Introduction to Functional Web Architectures (cont.) 1113 – 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 without the disadvantages of potential large bandwidth and trusted application issues McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11.1 An Introduction to Functional Web Architectures (cont.) 1114 – Summary • For business logic, a combination of Option and are most common • Option 2, client-side script, is used for data validation and other nonproprietary processing • Option 4, server-side script, protects the privacy of scripts • Option is ideal for database support McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 1115 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 1116 11.1 An Introduction to Functional Web Architectures (cont.) – Option 3: Send a Set of Records to Client for Further Processing • Similar to Option • Data from the server is processed directly by the browser McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 1117 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 1118 11.2 ASP.NET Web Applications 1119 • 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, in your textbook McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11.2 ASP.NET Web Applications (cont.) • Validating User Input – Validator controls for Web Forms provide the means for checking the contents of other controls – Each input control can have zero or more associated validators – Validators can perform on the client or server McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 1120 11.2 ASP.NET Web Applications (cont.) • Validation Controls for Web Forms Type of Validation Control to Use Required entry Comparison to a value Range checking Pattern matching RequiredFieldValidator CompareValidator RangeValidator RegularExpressionValidator User-defined CustomValidator McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 1121 11.2 ASP.NET Web Applications (cont.) 1122 – Complete Example 11.2, Validating User Input, in your textbook McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 11.3 Using Databases with Web Applications • Complete the examples listed below in your textbook: – Example 11.3 Using a DataGrid to Display Data on a Web Form – Example 11.4 Editing Data Using a DataGrid Component – Example 11.5 Using XML and XSL with Web Form McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 1123 Chapter Summary 1124 • 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved Chapter Summary (cont.) 1125 • Complex and/or proprietary business logic typically should be done on the server • Data management is typically handled on a server • Visual Basic NET supports Web Application projects • The Web Form is the primary component in Web Application projects McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved Chapter Summary (cont.) 1126 • 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 McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved Chapter Summary (cont.) • XML processing is available to the Web Form • Visual Basic NET provides methods to maintain a session within ASP.NET McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 1127 ... critical to application success McGraw Hill/Irwin ©2002 by The McGraw-Hill Companies, Inc All rights reserved 111 8 11. 2 ASP .NET Web Applications 111 9 • Creating a Simple Web Application – Visual Basic. .. 11- 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. .. 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,