Home > Articles > Programming > Windows Programming

  • Print
  • + Share This
Like this article? We recommend Implementing the Custom Paging Mechanism

Implementing the Custom Paging Mechanism

To reproduce the paging mechanism, you need some buttons and some label/text boxes. Usually labels and text boxes are added to screens automatically to display or edit data, but you have a chance to add controls that are not data-bound to the original collection and that you can use for your own purposes. To accomplish this goal, you use the so-called "local properties."

  1. With the screen designer open, click Add Data Item. In the Add Data Item dialog, select the Local Property option. Make sure that the Is Required checkbox is unselected (see Figure 7).
  2. The new property is called CurrentPage, and it represents the current page in the data collection. We'll use this property to write a different page number for moving easily to another page.
  3. The CurrentPage property is visible on the left side of the designer. Drag it onto the designer surface and release it under the Columns Layout you created earlier (see Figure 8).
  4. Create a local property called PageNumber, of type String, not required. Drag the new property onto the screen designer, but change its appearance to make it a label instead of a text box (see Figure 9). This property will contain the number of total pages. Both properties will be populated in code.

Now it's time to add some buttons to control the navigation between pages. In particular, you need four buttons to let the user move to the first page, the last page, the next page, and the previous page.

  1. Expand the Command Bar element located under the Custom Control. Here you'll find three built-in buttons that perform data operations over the bound collection (see Figure 10).
  2. Start by adding a new button. You must specify a name for a method that will be associated to the button, as shown in Figure 11. For each button you'll handle later, you need both the Execute and CanExecute method hooks.
  3. Associate the methods FirstPage, LastPage, NextPage, and PreviousPage to their related buttons. You can also change each button's appearance from the classic layout to the hyperlink layout (refer to Figure 10).
  4. Click Write Code in the screen designer.

The rest of the work must be done inside the code editor. At startup, the application must get a reference to the text box that shows the current page number and that allows changing the page (other than setting up initial values). This functionality requires interacting with the Silverlight infrastructure and is performed by the code shown in Listing 2, which is commented for easier reading.

Listing 2—Handling the changing of pages.

'Hold a reference to the text box where page number can be changed
Private changePageBox As Windows.Controls.TextBox
 
Private Sub EditableCustomersGrid_Created()
    'Return the specified control in a LightSwitch fashion
    Dim pageBox = Me.FindControl("CurrentPage")
 
    'Subscribe to the ControlAvailable event and get
    'the real control via the e.Control property
    AddHandler pageBox.ControlAvailable, Sub(sender As Object, e As ControlAvailableEventArgs)
                                             Me.changePageBox = CType(e.Control, Windows.Controls.TextBox)
 
                                             'When the user press Enter, retrieve the page number (if valid)
                                             'and change the current page
                                             AddHandler Me.changePageBox.KeyUp, Sub(senderK As Object, eK As Windows.Input.KeyEventArgs)
                                                                                    If eK.Key = Windows.Input.Key.Enter Then
                                                                                        Dim pageNumber As Integer
                                                                                        If Integer.TryParse(Me.changePageBox.Text, pageNumber) Then
                                                                                            Me.Customers.Details.PageNumber = pageNumber
                                                                                            Me.PageNumber = " of " + CStr(Me.Customers.Details.PageCount)
                                                                                            Me.CurrentPage = CStr(pageNumber)
                                                                                        End If
 
                                                                                    End If
                                                                                End Sub
                                         End Sub
 
    'Set values at startup
    Me.CurrentPage = "1"
    Me.PageNumber = " of " + CStr(Me.Customers.Details.PageCount)
End Sub

Everything goes around the Details property of a collection, which also exposes the PageCount and PageNumber properties. These properties allow obtaining the number of total pages for the collection and setting the current page. Notice that the PageNumber label is populated with an informational message showing the total number of pages.

Now let's move on to writing code for the FirstPage and LastPage methods. These methods are the simplest of the set, since you only need to set the page number and update the displayed text. Listing 3 shows the code for this task:

Listing 3—Implementing navigation to the first page and the last page.

Private Sub FirstPage_Execute()
    Me.Customers.Details.PageNumber = 1
    Me.CurrentPage = CStr(Me.Customers.Details.PageNumber)
    Me.PageNumber = " of " + CStr(Me.Customers.Details.PageCount)
End Sub


Private Sub LastPage_Execute()
    Me.Customers.Details.PageNumber = Me.Customers.Details.PageCount
    Me.CurrentPage = CStr(Me.Customers.Details.PageNumber)
    Me.PageNumber = " of " + CStr(Me.Customers.Details.PageCount)
End Sub

It's easy to move to the first and last page by setting the Details.PageNumber property of the collection. You don't need to handle CanExecute for these buttons, since a collection always has a first page and a last page.

Things are a little bit different for the NextPage and PreviousPage methods, whose code is shown in Listing 4.

Listing 4—Implementing navigation to the next page and the previous page.

Private Sub NextPage_Execute()
    Me.Customers.Details.PageNumber += 1
    Me.CurrentPage = CStr(Me.Customers.Details.PageNumber)
    Me.PageNumber = " of " + CStr(Me.Customers.Details.PageCount)
End Sub


Private Sub NextPage_CanExecute(ByRef result As Boolean)
    result = (Me.Customers.Details.PageNumber < Me.Customers.Details.PageCount)
End Sub


Private Sub PreviousPage_Execute()
    Me.Customers.Details.PageNumber -= 1
    Me.CurrentPage = CStr(Me.Customers.Details.PageNumber)
    Me.PageNumber = " of " + CStr(Me.Customers.Details.PageCount)
End Sub

Private Sub PreviousPage_CanExecute(ByRef result As Boolean)
    result = Me.Customers.Details.PageNumber > 1
End Sub

As you can see, it's still easy to move to the next or previous page, simply by increasing or decreasing the page number. However, you need to ensure that the action is possible by handling CanExecute and calculating the current position. If the result of the evaluation is False, the button will be disabled automatically until the result becomes True.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020