Chapter 13 Advanced Web Forms with Databases

Programming Right From the Start with Visual Basic.NET

CHAPTER 13

Advanced Web Forms with Databases

True-False Questions

1. ADO.NET and ASP.NET are tools used to create three-tier application architecture. Answer: True Level: Easy Section: 13-1 Page: 345

2. The typical three-tier architecture has the database as the middle tier. Answer: False Level: Easy Section: 13-1 Page: 345

3. A medium client refers to the application layer. Answer: False Level: Moderate Section: 13-1 Page: 345

4. The logical layer acts as a mediator between the user and the database. Answer: False Level: Moderate Section: 13-1 Page: 345

5. A web browser is a good example of a thin client. Answer: True Level: Easy Section: 13-1 Page: 345

6. Business logic stored in a web server module is easy to maintain and modify. Answer: True Level: Moderate Section: 13-1 Page: 345

7. A disadvantage of using an application layer is that the number of connections is less than if users connected directly with the database. Answer: False Level: Moderate Section: 13-1 Page: 345

8. The three-tier architecture can help to conserve network and server resources. Answer: True Level: Moderate Section: 13-1 Page: 346

9. No more than two computers may be placed in a server farm. Answer: False Level: Easy Section: 13-1 Page: 346

10. A three-tier architecture can exist on a single computer. Answer: True Level: Easy Section: 13-1 Page: 346

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11. The two types of methods for tracking the state of a web page are client-side and data-side. Answer: False Level: Easy Section: 13-2 Page: 346

12. A web server needs special techniques to know the state of previous web pages. Answer: True Level: Easy Section: 13-2 Page: 346

13. The only way to store information about the state of a web page is to store it on a client machine. Answer: False Level: Easy Section: 13-2 Page: 346

14. Client-side state management techniques cannot be changed by the end user. Answer: False Level: Easy Section: 13-3 Page: 346

15. The view state is always stored on the client machine. Answer: False Level: Moderate Section: 13-3 Page: 347

16. The information about a page’s view state is visible in the HTML source. Answer: True Level: Moderate Section: 13-3 Page: 347

17. The length of a query string is limited to 128 characters. Answer: False Level: Easy Section: 13-3 Page: 347

18. A query string is information stored at the end of a URL. Answer: True Level: Easy Section: 13-3 Page: 347

19. Query strings are the most secure type of state management technique. Answer: False Level: Moderate Section: 13-3 Page: 347

20. Using cookies is unreliable because users can refuse to have them stored on a machine. Answer: True Level: Easy Section: 13-3 Page: 347

21. Cookies are attached to a web page before being sent to the browser. Answer: False Level: Moderate Section: 13-3 Page: 347

22. An appliance state is an example of a server-side state management technique. Answer: False Level: Moderate Section: 13-4 Page: 348

23. Server-side state management techniques should be used to keep sensitive information secure. Answer: True Level: Easy Section: 13-4 Page: 348

24. The application variable can be accessed by any code in any file in a web application. Answer: True Level: Easy Section: 13-4 Page: 348

25. The key term Application.VariableName is used to read or write to an application variable. Answer: False Level: Moderate Section: 13-4 Page: 348

26. An application variable is dimensioned like all other variables. Answer: False Level: Hard Section: 13-4 Page: 348

27. The syntax for creating a session variable is similar to that for creating an application variable. Answer: True Level: Easy Section: 13-4 Page: 349

28. All browsers share the same session variables. Answer: False Level: Easy Section: 13-4 Page: 349

29. Using a database means that no state information will be lost if all web servers are turned off for maintenance. Answer: True Level: Moderate Section: 13-4 Page: 349

30. A database can efficiently store state information for high volume web applications. Answer: True Level: Easy Section: 13-4 Page: 350

Multiple Choice Questions

31. Which is not a fundamental service identified in a three-tier architecture? a.) Association layer b.) Connection layer c.) Logical layer d.) Both a and b. e.) All of the above.

Answer: e Level: Moderate Section: 13-1 Page: 345

32. Which layer is exemplified by a web server? a.) Application b.) Association c.) Data d.) Logical e.) Presentation

Answer: a Level: Easy Section: 13-1 Page: 345

33. Which layer is exemplified by a fat client? a.) Application b.) Association c.) Data d.) Logical e.) Presentation

34. Which layer is exemplified by the use of ADO.NET? a.) Application b.) Association c.) Data d.) Logical e.) Presentation

Answer: c Level: Moderate Section: 13-1 Page: 345

35. How will using a middle tier typically affect the number of connections to a database? a.) Increase the number b.) Have no effect on the number c.) Decrease the number d.) It depends on the type of client. e.) It depends on the type of database.

Answer: c Level: Hard Section: 13-1 Page: 345

36. An application layer: a.) will contain business logic. b.) manage connections to the database. c.) can be distributed over many computers. d.) Both a and b. e.) All of the above.

37. A data layer is responsible for: a.) retrieving information from a database. b.) updating information in a database. c.) deleting information in a database. d.) Both a and b. e.) All of the above.

Answer: e Level: Easy Section: 13-1 Page: 345

38. What is the minimum number of computers in a three-tier architecture? a.) 0 b.) 1 c.) 2 d.) 3 e.) 4 or more

Answer: b Level: Easy Section: 13-1 Page: 346

39. A server farm is: a.) an example of a distributed application. b.) makes it easy to add new computers if demand increases. c.) applies only to web servers. d.) Both a and b. e.) All of the above.

Answer: d Level: Moderate Section: 13-1 Page: 346

40. Which is a valid type of state management for the creation of web pages? a.) Client side b.) Server side c.) Data side d.) Both a and b. e.) All of the above.

Answer: d Level: Easy Section: 13-2 Page: 346

41. The stateless HTTP protocol refers to web pages created: a.) on a web server. b.) without information from a database. c.) without knowledge of previous web pages. d.) before a request from a client. e.) on a client machine.

42. Client-side state management techniques are appropriate when using: a.) sensitive information. b.) critical applications. c.) an intranet. d.) Both a and b. e.) All of the above.

43. Where does the view state store information? a.) HTML source b.) Text file c.) URL d.) Both a and b. e.) All of the above.

Answer: a Level: Moderate Section: 13-3 Page: 347

44. Where does the query string store information? a.) HTML source b.) Text file c.) URL d.) Both a and b. e.) All of the above.

45. Where do cookies store information? a.) HTML source b.) Text file c.) URL d.) Both a and b. e.) All of the above.

Answer: b Level: Moderate Section: 13-3 Page: 347

46. Which client-side technique is specific to ASP.NET? a.) Cookies b.) Query string c.) View state d.) Both a and b. e.) All of the above.

47. Which client-side technique can be disabled by the end-user? a.) Cookies b.) Query string c.) View state d.) Both a and b. e.) All of the above.

Answer: a Level: Moderate Section: 13-3 Page: 347

48. What symbol specifies the beginning of a query string? a.) @ b.) # c.) $ d.) % e.) ?

Answer: e Level: Easy Section: 13-3 Page: 347

49. What is the syntax for creating and using an application variable? a.) Application.VariableName = Value b.) Application.VariableName = (Value) c.) Application(VariableName) = Value d.) Application(VariableName) = (Value) e.) Application(“VariableName”) = Value

50. Which server-side technique is available in ASP.NET? a.) Application states b.) Session states c.) Database support d.) Both a and b. e.) All of the above.

Answer: d Level: Easy Section: 13-4 Page: 349

51. An Application variable is created: a.) when the application is first placed on a web server. b.) when the web server is first started. c.) when the first client requests a URL resource. d.) every time a client requests a URL resource. e.) every time a new client interacts with the web application.

52. A Session variable is created: a.) when the application is first placed on a web server. b.) when the web server is first started. c.) when the first client requests a URL resource. d.) every time a client requests a URL resource. e.) every time a new client interacts with the web application.

53. If there is no activity from a browser, how long will a session variable last? a.) 10 minutes b.) 20 minutes c.) 60 minutes d.) 100 minutes e.) 200 minutes

Answer: b Level: Easy Section: 13-4 Page: 349

54. Which is not a reason for using a database to store state information? a.) The capacity to store high volumes of information b.) The ability to use data mining techniques on the stored information c.) The ability to use application and session variables d.) Security from unauthorized use e.) The power to easily query for specific information

Fill in the Blank Questions

55. Most applications can be partitioned into three logical layers: ___presentation___, application___, and ___data___ layers. Level: Easy Section: 13-1 Page: 344

56. In a three-tier system architecture an Access database represents the ___data___ layer. Level: Easy Section: 13-1 Page: 345

57. In a three-tier system architecture a web browser represents the ___presentation___ layer. Level: Easy Section: 13-1 Page: 345

58. In a three-tier system architecture an IIS Web server represents the ___application___ layer. Level: Easy Section: 13-1 Page: 345

59. A(n) ___fat client___ refers to a user’s computer that has a substantial processing load. Level: Moderate Section: 13-1 Page: 345

60. Mobile computing devices run as a(n) ___thin client___ user layer architecture. Level: Moderate Section: 13-1 Page: 345

61. Changing business rules is easy when they are contained in modules located in the ___application___ layer. Level: Moderate Section: 13-1 Page: 345

62. The ___application___ layer shields the end user from the details of using the database. Level: Moderate Section: 13-1 Page: 345

63. A(n) ___server farm___ is a collection of computers that share the work of an application or data layer. Level: Moderate Section: 13-1 Page: 346

64. The protocol for creating web pages is ___stateless___ because new pages are created without information about the previous web pages. Level: Hard Section: 13-2 Page: 346

65. The technique of ___state management___ is the process of storing information over multiple web page requests. Level: Moderate Section: 13-2 Page: 346

66. Storing information about previous web pages on the ___client___ side is best done with secure, intranet applications. Level: Moderate Section: 13-2 Page: 346

67. Cookies are an example of ___client side___ state management. Level: Easy Section: 13-3 Page: 346

68. ASP.NET can save the state of a page as a part of the ___view state___ facility. Level: Moderate Section: 13-3 Page: 347

69. The information in a(n) ___query string___ is visible in the web page’s URL. Level: Moderate Section: 13-3 Page: 347

70. Information about a web page that is stored in a text file is called a(n) ___cookie___. Level: Moderate Section: 13-3 Page: 347

71. The ___application___ state holds information for the life of a web application. Level: Moderate Section: 13-4 Page: 348

72. The first request for a URL resource generates the ___application state___. Level: Moderate Section: 13-4 Page: 348

73. The key term for creating an application variable is ___Application___. Level: Easy Section: 13-4 Page: 348

74. Each ___browser___ that requests a web application gets its own session state. Level: Moderate Section: 13-4 Page: 349

75. The key term for creating a session variable is ___Session___. Level: Easy Section: 13-4 Page: 349

76. Session variables will be lost after ___20 minutes___ inactivity. Level: Moderate Section: 13-4 Page: 349

77. Increase security is an advantage of the ___database___ server-side state management technique. Level: Moderate Section: 13-4 Page: 350

78. Application layers are ___worse__ than data layers at storing large volumes of state information. Level: Moderate Section: 13-4 Page: 350

79. State information store in a database is considered ___persistent___ because it is less prone to server crashes than web servers. Level: Hard Section: 13-4 Page: 350

Essay Questions

80. Identify and describe the layers of a three-tier architecture.

The three-tier architecture breaks the logic of an application into three modules, called layers. These layers are Presentation, Application, and Data. Physically these three layers can reside on the same computer or three separate computers. The design of the architecture is a conceptual division of functionality.

The Presentation layer is the part of the application that the end user sees and interacts with. It hides the details of the other layers and makes the application easy to use. This layer can be a Windows form processing data locally on a client’s computer (fat client) or an internet browser with displaying an ASP.NET Web form (thin client).

The Application layer has two main functions: to process business rules and interact with the data layer. This layer typically is a web server that delivers web pages to a browser, but it can also be an application server on an intranet that communicates to with the Windows form presentation layer. The advantage of the application layer is that changes in business rules (a new state tax rate) require changes on a few application servers, rather than the thousands of computers that hold the presentation layer.

The Data layer is where all of the information vital to the business is stored. Typically this is done is a database, but flat files (text files) can be used as well. It is best to use databases because they are designed to accurately modify (add, delete, edit) and retrieve (query) data. The fact that only the application layer interacts with the database increases the security of the information stored in the data layer.

81. What is State Management? Describe and give examples of the two types of State Management techniques.

State management is the storage of information about web pages each time a user accesses a web server. This is important because one web server is designed to serve many clients and the HTTP protocol does not require that the state of each web page be remembered. When a server farm of web servers is used, it is possible that each request to the web site will go to a different computer

13 - 11 Chapter 13 – Advanced Web Forms with Databases making it impossible for one web server to know what web page the other web server just sent out.

One method to store the state of a web page is to embed the information on the Client (end user’s) machine in the form of a View State, Query String, or Cookie. The View State is a feature provided by ASP.NET which will store information about the state of the web page in the HTML source. The Query String is information stored in the URL address (identified with a ?). A Cookie is a text file stored on the client’s computer. Because the information store with these techniques is accessible by the end user, client-side techniques should not be used to store vital or sensitive information.

The other method to store the state of a web page is to store the information on a server. This can be either a web server in the form of Application or Session variables, or on a database server. Both methods are better at keeping data secure.

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