Controls

This chapter is from the book

MCAD Developing and Implementing Web Applications with Microsoft Visual Basic .NET and Microsoft Visual Studio .NET Exam Cram 2 (Exam Cram 70-305)

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This chapter is from the book

This chapter is from the book 

MCAD Developing and Implementing Web Applications with Microsoft Visual Basic .NET and Microsoft Visual Studio .NET Exam Cram 2 (Exam Cram 70-305)

Learn More Buy

Exam Prep Questions

Question 1

You are designing a new page for your ASP.NET Web Application from scratch. The page will display statistical information in a series of tables and text fields, but will not require any user input. The page will carry out complex calculations to determine the validity of the information that it displays. Which controls should you use to build the user interface for this page?

1. HTML controls

2. HTML server controls

3. Web server controls

4. Validation controls

Answer C is correct. Web server controls are designed for easy programmability on ASP.NET pages. Answer A is incorrect because you can't use code-behind to easily specify the values to display in HTML controls. Answer B is incorrect because HTML server controls are mainly used to upgrade existing ASP pages, not to create new pages. Answer D is incorrect because validation controls are only useful when there is user input to validate.

Question 2

You have developed an ASP.NET Web Form that allows users to select from a list of replacement parts to order. The Web Form uses the following code to load the list into a control:

Private Sub Page_Load(ByVal sender As System.Object, _
 ByVal e As System.EventArgs) Handles MyBase.Load
  lbParts.Items.Add("Flange")
  lbParts.Items.Add("Motor")
  lbParts.Items.Add("Bracket")
End Sub

As users select parts, you execute code on the Web server to move the selected parts to a second list. Users report that the page initially displays correctly, but after they select one part, the original list reads as follows:

Flange
Motor
Bracket
Flange
Motor
Bracket

How should you modify the code to prevent this from happening?

1. Private Sub Page_Load(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles MyBase.Load
     If lbParts.Items.Count < 3 Then
       lbParts.Items.Add("Flange")
       lbParts.Items.Add("Motor")
       lbParts.Items.Add("Bracket")
     End If
   End Sub

2. Private Sub Page_Load(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles MyBase.Load
     If Not IsPostBack Then
       lbParts.Items.Add("Flange")
       lbParts.Items.Add("Motor")
       lbParts.Items.Add("Bracket")
     End If
   End Sub

3. Private Sub Page_Load(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles MyBase.Load
     If IsPostBack Then
       lbParts.Items.Add("Flange")
       lbParts.Items.Add("Motor")
       lbParts.Items.Add("Bracket")
     End If
   End Sub

4. Private Sub Page_Load(ByVal sender As System.Object, _
    ByVal e As System.EventArgs) Handles MyBase.Load
     lbParts.Items.Clear
     lbParts.Items.Add("Flange")
     lbParts.Items.Add("Motor")
     lbParts.Items.Add("Bracket")
   End Sub

Answer B is correct. You can use the IsPostBack property to tell whether the page is being loaded for the first time and then only perform initializations on the first load. Answers A and D are incorrect because they will reinitialize the ListBox every time that the page is loaded, slowing down the page rendering. Answer C is incorrect because the postback test should be looking for False, not True.

Question 3

You have designed a Web Form that includes a Panel control named Panel1. Under some circumstances, you want to dynamically display a TextBox control on this Panel control. Your form includes the following code:

Dim txtNew As TextBox = New TextBox
txtNew.ID = "txtNew"
txtNew.Text = "Dynamic TextBox"

When you run the code, the form does not display the new TextBox. You single-step through the code and verify that these lines are being executed. How should you fix this problem?

1. Dim txtNew As TextBox = New TextBox
   txtNew.ID = "txtNew"
   txtNew.Text = "Dynamic TextBox"
   txtNew.Enabled = True

2. Dim txtNew As TextBox = New TextBox
   txtNew.ID = "txtNew"
   txtNew.Text = "Dynamic TextBox"
   txtNew.Visible = True

3. Dim txtNew As TextBox = New TextBox
   txtNew.ID = "txtNew"
   txtNew.Text = "Dynamic TextBox"
   Panel1.Controls.Add("txtNew")

4. Dim txtNew As TextBox = New TextBox
   txtNew.ID = "txtNew"
   txtNew.Text = "Dynamic TextBox"
   Panel1.Controls.Add(txtNew)

Answer D is correct. To show a dynamically created control on a Web Form, you must add the new control to the Controls collection of a container control such as a Panel. Answers A and B are incorrect because they alter the properties of the control without adding it to a container. Answer C is incorrect because the Add method requires an object reference, not a String with an object name.

Question 4

You are designing a Web page for your corporate intranet. All the users on the intranet are using either Internet Explorer 5.0 or Internet Explorer 6.0 as their browser. When an employee enters his employee number, you need to validate it as a legitimate employee number so that you can audit actions on the Web site. Which type of validation should you perform, if any?

1. You should not validate this data.

2. You should only perform client-side validation.

3. You should only perform server-side validation.

4. You should perform both client-side and server-side validation.

Answer D is correct. You should validate the data in this scenario because the correct data is critical to the application. You should use client-side validation because client-side validation is the fastest way to catch accidental errors in the data and can prevent bad data from reaching the server. However, you should also use server-side validation to eliminate the possibility of someone hand-crafting an HTTP request to bypass the client-side validation.

Question 5

You are designing a new home page for your company, using ASP.NET. The home page will have numerous graphics, including the company logo, images used for navigation, and pictures of your company's graphics. You want to make sure that users who cannot view graphics (for example, those browsing with a screen reader) receive a description of each image instead. Which property of the Image control should you set to provide this description?

1. Attributes property

2. ToolTip property

3. AlternateText property

4. ImageUrl property

Answer C is correct. The AlternateText property of an Image control supplies text that is used by screen readers and by other browsers when an image cannot be displayed. Answer A is incorrect because the Attributes property returns an array of attributes of the control. Answer B is incorrect because the ToolTip property only supplies text to be seen when the mouse is hovered over the control. Answer D is incorrect because the ImageUrl property tells the control which image to display.

Question 6

You are designing a Web Form that will allow the user to specify a date for a dental appointment. You want to allow the user to specify a date by choosing it from a calendar. The users of the application employ a wide variety of Web browsers, including Internet Explorer versions 3.2 through 6.0 and Netscape versions 4.79 through 7.0. How should you proceed to create this page with the least effort?

1. Work directly in HTML view of your Web form. Design the calendar using HTML tags.

2. Work in Design view of the Web form. Design the calendar by using the Table, TableRow, and TableCell Web server controls.

3. Work in Design view of the Web form. Design the calendar by using a single Calendar control.

4. Work in the code-behind file. Design the calendar by dynamically adding HTML controls to the Web Form at runtime.

Answer C is correct. ASP.NET will render complex controls such as the Calendar control properly for both uplevel and downlevel browsers by detecting the browser and sending the appropriate HTML markup. Answers A, B, and D are incorrect because they all require substantially more work than using a single Calendar control.

Question 7

Your company has an existing classic ASP application that is used to track news on your intranet. You have been tasked with upgrading the application to ASP.NET. As a first step, you want to keep the user interface the same, but move the business logic to code-behind files. How should you proceed?

1. Continue to use HTML controls on ASP.NET Web Forms. In the code-behind files, rewrite all business logic using Visual Basic .NET.

2. Use ASP.NET Web server controls instead of HTML controls. In the code-behind files, rewrite all business logic using Visual Basic .NET.

3. Apply the runat="server" attribute to all HTML controls. In the code-behind files, rewrite all business logic using Visual Basic .NET.

4. Continue to use HTML controls for labels and textboxes, but convert all button controls to Web server controls. In the code-behind files, rewrite all business logic using Visual Basic .NET.

Answer C is correct. Applying the runat="server" attribute is the only step required to make the controls on the page available to code in a code-behind file. Answers A and D are incorrect because you cannot use code-behind files to manipulate HTML controls. Answer B is incorrect because there is no built-in way to directly convert HTML controls to Web server controls.

Question 8

You are designing a Web Form that includes four RadioButton controls named rb1, rb2, rb3, and rb4. Users should be able to select either rb1 or rb2, and either rb3 or rb4. How should you configure the controls to achieve this?

1. Place rb1 and rb2 on a Panel control named pnlA. Place rb3 and rb4 on a Panel control named pnlB.

2. Set the GroupName property of rb1 and rb2 to "Group1". Set the GroupName property of rb3 and rb4 to "Group2".

3. Set the Parent property of rb2 to rb1. Set the Parent property of rb4 to rb3.

4. Set the AutoPostBack property of rb1 and rb3 to True. Set the AutoPostBack property of rb2 and rb4 to False.

Answer B is correct. RadioButton controls that share a GroupName are mutually exclusive. Answer A is incorrect because placing the controls on different panels organizes them visually, but does not put them in distinct groups. Answer C is incorrect because the Parent property is just a link to the form containing the controls. Answer D is incorrect because AutoPostBack indicates whether the Web Form should be posted when the control is clicked.

Question 9

You want to keep consistent formatting for all the Web Forms in your application. To achieve this, you have created a cascading style sheet named CompanyStyle.css and have linked it to all the Web pages. You have defined a style class named ButtonStyle in CompanyStyle.css to format buttons on the Web Forms. Which of the following property settings would you use with a Button Web server control to use the ButtonStyle style class?

1. Style="ButtonStyle"

2. Style=".ButtonStyle"

3. CssClass="ButtonStyle"

4. CssClass=".ButtonStyle"

Answer C is correct. The CssClass property specifies the CSS style class to apply to a particular control. Answers A and B are incorrect because the Style property is used to supply CSS attributes directly, rather than the name of a CSS style. Answers B and D are incorrect because styles are referred to without the leading dot, even though you must use the dot when defining them in a CSS file.

Question 10

You are designing a Web Form to collect user registration information for your corporate Web site. You want to ensure that users supply a value for the Age TextBox control and that the value supplied is between 18 and 105. Which validation control should you use (select all that apply)?

1. RequiredFieldValidator

2. RangeValidator

3. RegularExpressionValidator

4. CustomValidator

Answers A and B are correct. You can use the RequiredFieldValidator control to ensure that the user enters a value and the RangeValidator control to check that the value is in the correct range. Although you could use the RegularExpressionValidator or CustomValidator controls to check the range, doing so would require you to write a complex regular expression or custom business logic, so answers C and D are incorrect.

Question 11

Your Web Form displays a list of State names in a DropDownList control. As soon as the user selects a state, you want to update a Label control to display the appropriate sales tax rate. You have written custom logic to do so in the SelectedIndexChanged event handler for the control. What property should you set to ensure that this event is handled at the correct time?

1. EnableViewState = True

2. AutoPostBack = False

3. EnableViewState = False

4. AutoPostBack = True

Answer D is correct. By default, selection change events for list controls are not sent to the server until the Web Form is posted by some other means (for example, by the user clicking a Submit button). Setting the AutoPostBack property to True causes the postback to happen as soon as a new item is selected in the list. Answer B is incorrect because it uses the wrong AutoPostBack value. Answers A and C are incorrect because the EnableViewState property has no effect on the timing of postbacks.

Question 12

Your Web Form requires the user to enter an email address. Which control should you use to validate the contents of the TextBox containing the email address?

1. RequiredFieldValidator

2. RegularExpressionValidator

3. RangeValidator

4. CustomValidator

Answer B is correct. The RegularExpressionValidator control is suited to checking input that conforms to a particular pattern such as a date or an email address (and .NET has a built-in expression for email addresses). Answer A is incorrect because the RequiredFieldValidator ensures that data was entered, but does not check the contents of the data. Answer C is incorrect because the RangeValidator checks to see that data is between a pair of values. Answer D is incorrect because the CustomValidator requires you to write extra code to perform the same tasks that the RegularExpressionValidator has built in.