© Copyright 1992-2004 by Deitel & Associates, Inc. and Pearson Education Inc. All Rights Reserved. 1 Tutorial 12 – Security Panel Application Introducing.

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© Copyright 1992-2004 by Deitel & Associates, Inc. and Pearson Education Inc. All Rights Reserved.

Tutorial 12 – Security Panel Application

Introducing the Select Case Multiple-Selection Statement

Outline

12.1 Test-Driving the Security Panel Application12.2 Introducing the Select Case Multiple-Selection Statement12.3 Constructing the Security Panel Application12.4 Wrap-Up

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Objectives

• In this tutorial, you will learn to:– Use the Select Case multiple-selection statement.

– Use Case statements.

– Use the Is keyword.

– Display a date and time.

– Use TextBox property PasswordChar.

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12.1 Test-Driving the Security Panel Application

Application Requirements A lab wants to install a security panel outside a laboratory room. Only authorized personnel may enter the lab, using their security codes. The following are valid security codes (also called access codes) and the groups of employees they represent: Values Groups 1645–1689 Technicians 8345 Custodians 9998, 1006–1008 Scientists Once a security code is entered, access is either granted or denied. All access attempts are written to a window below the keypad. If access is granted, the date, time and group (scientists, custodians, etc.) are written to the window. If access is denied, the date, the time and a message, “Access Denied,” are written to the window. Furthermore, the user can enter any one-digit access code to summon a security guard for assistance. The date, the time and a message, “Restricted Access,” are then written to the window to indicate that the request has been received.

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• Load the Wage Calculator application– Debug > Start

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Figure 12.1　 Security Panel application executing.

TextBox

Output ListBox

Keypad

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Figure 12.2　 Asterisks displayed in Security code: field.

An asterisk is displayed for each numeric key pressed

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• Entering invalid code– Enter 1212

– Click # Button

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Figure 12.3　 Security Panel displaying Access Denied message.

Message indicating that an invalid security code was entered

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• Entering valid code– Enter 1006– Click # Button

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Figure 12.4 　 Security Panel application confirming a valid security-code entry.

Message displayed when a valid security code is entered

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12.2 Introducing the Select Case Multiple-Selection Statement

• Select Case statement– Begins with keywords Select Case followed by test

expression

– Can contain optional Case Else statement– Terminates with keywords End Select

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12.2 Introducing the Select Case Multiple-Selection Statement

display "Excellent!"

[strGrade = "A"]

[strGrade <> "A"]

[strGrade = "B"]

[strGrade = "F"]

.

.

Case "A"

case b

Case "F"

C ase "B" display "Very good!"

display "Failure."

display "Inva lid grade."

[strGrade <> "B"]

[strGrade <> "F"]

Figure 12.5 Select Case multiple-selection statement UML activity diagram.

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12.3 Constructing the Security Panel Application

Action Control Event Label the application’s fields lblSecurityCode,

lblAccessLog

btnEnter Click

Retrieve security code input by user txtSecurityCode

Clear input TextBox txtSecurityCode

Select correct Case based on access code

Case where access code is less than 10 Store text “Restricted Access”

Case where access code is in the range 1645 to 1689 Store text “Technicians”

Figure 12.6 ACE table for Security Panel application.

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Action Control Event Case where access code equals 8345

Store text “Scientists”

Case where access code equals 9998 or is in the range 1006 to 1008 Store text “Scientists”

Case where none of preceding Cases match Store text “Access Denied”

Display message in ListBox with current time and String variable’s contents

lstLogEntry

Figure 12.6 ACE table for Security Panel application.

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Figure 12.7 Variable declarations for btnEnter_Click.

Declaring event handler’s variables

• Declaring variables

• Clearing the TextBox

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• Creating Case statement– Specify a range of values using:

• Keyword Is

• Comparison operator (in this case, <)

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Figure 12.8　 Select Case statement.

Creating a Select Case

statement

• Create Select Case statement

– Set controlling expression

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Figure 12.9　 First Case added to Select Case statement.

Is keyword can be used for relational and equality comparisons

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• Creating a Case statement– Specifying a range of values using:

• Keyword To

– Checking for a specific number

– Specifying multiple expressions• Use a comma to separate expressions

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Figure 12.10　 Cases specified for remaining access codes.

To keyword can be used to specify a range of

values to test.

Comma used to separate multiple expressions in a Case

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• Creating a Case Else statement– Use keywords Case Else

– Must follow all other Case statements

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Figure 12.11　 Case Else of the Select Case statement.

Case Else statement executes when no other

Case matches

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• Date structure– Stores and displays date and time information

– Property Now returns:• System time as a Date

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Figure 12.12 Updating the Security Panel application’s ListBox.

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Figure 12.13 Event handler btnZero_Click.

• Appending “0” to the end of a String

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Figure 12.14 Event handlers btnOne_Click and btnTwo_Click.

• Appending “1” and “2” to the end of a String

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Figure 12.15 Event handler btnClear_Click defined.

• Clearing the TextBox

Outline28


1 Public Class FrmSecurityPanel

2 Inherits System.Windows.Forms.Form

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4 ' Windows Form Designer generated code

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6 Private Sub btnEnter_Click(ByVal sender As System.Object, _

7 ByVal e As System.EventArgs) Handles btnEnter.Click

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9 Dim intAccessCode As Integer ' stores access code entered

10 　　　　　　　　　　　　　　　　Dim strMessage As String ' displays access status of users

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12 intAccessCode = Val(txtSecurityCode.Text)

13 　　　 txtSecurityCode.Clear()

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15 　 Select Case intAccessCode ' check access code input

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17 ' access code less than 10

18 Case Is < 10

19 strMessage = "Restricted Access"

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21 ' access code between 1645 and 1689

22 Case 1645 To 1689

23 strMessage = "Technicians"

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SecurityPanel.vb(1　of　5)

Retrieving access code and clearing TextBox

Declaring variables

Using a Select Case statement to determine user access level

Outline29


25 ' access code equal to 8345

26 Case 8345

27 strMessage = "Custodians"

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29 ' access code equal to 9998 or between

30 ' 1006 and 1008, inclusive

31 Case 9998, 1006 To 1008

32 strMessage = "Scientists"

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34 ' if no other Case is True

35 Case Else

36 strMessage = "Access Denied"

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38 End Select

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40 ' display time and message in ListBox

41 lstLogEntry.Items.Add(Date.Now & " " & strMessage)

42 End Sub ' btnEnter_Click

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44 Private Sub btnZero_Click(ByVal sender As System.Object, _

45 ByVal e As System.EventArgs) Handles btnZero.Click

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47 txtSecurityCode.Text &= "0" ' concatenate "0" to display

48 End Sub ' btnZero_Click

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Appending the numeric Button value to the text stored in the TextBox

Outline30


50 Private Sub btnOne_Click(ByVal sender As System.Object, _

51 ByVal e As System.EventArgs) Handles btnOne.Click

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54 End Sub ' btnOne_Click

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56 Private Sub btnTwo_Click(ByVal sender As System.Object, _

57 ByVal e As System.EventArgs) Handles btnTwo.Click

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60 End Sub ' btnTwo_Click

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62 Private Sub btnThree_Click(ByVal sender As System.Object, _

63 ByVal e As System.EventArgs) Handles btnThree.Click

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66 End Sub ' btnThree_Click

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68 Private Sub btnFour_Click(ByVal sender As System.Object, _

69 ByVal e As System.EventArgs) Handles btnFour.Click

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72 End Sub ' btnFour_Click

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Outline31


74 Private Sub btnFive_Click(ByVal sender As System.Object, _

75 ByVal e As System.EventArgs) Handles btnFive.Click

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78 End Sub ' btnFive_Click

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80 Private Sub btnSix_Click(ByVal sender As System.Object, _

81 ByVal e As System.EventArgs) Handles btnSix.Click

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84 End Sub ' btnSix_Click

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86 Private Sub btnSeven_Click(ByVal sender As System.Object, _

87 ByVal e As System.EventArgs) Handles btnSeven.Click

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90 End Sub ' btnSeven_Click

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92 Private Sub btnEight_Click(ByVal sender As System.Object, _

93 ByVal e As System.EventArgs) Handles btnEight.Click

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96 End Sub ' btnEight_Click

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Outline32


98 Private Sub btnNine_Click(ByVal sender As System.Object, _

99 ByVal e As System.EventArgs) Handles btnNine.Click

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102 End Sub ' btnNine_Click

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104 Private Sub btnClear_Click(ByVal sender As System.Object, _

105 ByVal e As System.EventArgs) Handles btnClear.Click

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107 txtSecurityCode.Clear() ' clear text from TextBox

108 End Sub ' btnClear_Click

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110 End Class ' FrmSecurityPanel


Clearing the TextBox

© Copyright 1992-2004 by Deitel & Associates, Inc. and Pearson Education Inc. All Rights Reserved. 1 Tutorial 12 – Security Panel Application Introducing.

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