Home > Articles > Microsoft > Other Microsoft

This chapter is from the book

Navigation Between Pages

Implement navigation for the user interface.

A typical Web application is a collection of Web pages linked to each other. In Chapter 2, I discussed the HyperLink control that allows a user to navigate to a different Web page when the hyperlink is clicked. However, there is also a need to navigate to a Web page programmatically. ASP.NET provides the following methods for programmatically navigating between pages:

  • Response.Redirect()

  • Server.Transfer()

  • Server.Execute()

I'll discuss each of these methods in the following sections.

The Response.Redirect() Method

The Response.Redirect() method causes the browser to connect to the specified URL. When the Response.Redirect() method is called, it creates a response whose header contains a 302 (Object Moved) status code and the target URL. When the browser receives this response from the server, it uses the header information to generate another request to the specified URL. When using the Response.Redirect() method, the redirection happens at the client side and involves two roundtrips to the server.

Using the Response.Redirect() method is recommended in the following cases:

  • You want to connect to a resource on ANY Web server.

  • You want to connect to a non-ASPX resource (such as an HTML file).

  • You want to pass query string as part of the URL.

The Server.Transfer() Method

The Server.Transfer() method transfers the execution from the current ASPX page to the specified ASPX page. The path specified to the ASPX page must be on the same Web server and must not contain a query string.

When the Server.Transfer() method is called from an executing ASPX page, the current ASPX page terminates execution and control is transferred to another ASPX page. The new ASPX page still uses the response stream created by the prior ASPX page. When this transfer occurs, the URL in the browser still shows the original page because the redirection occurs on the server side and the browser remains unaware of the transfer.

When you want to transfer control to an ASPX page residing on the same Web server, you should use Server.Transfer() instead of Response.Redirect() because Server.Transfer() will avoid an unnecessary roundtrip and provide better performance and user experience.

The default use of the Server.Transfer() method does not pass the form data and the query string of the original page request to the page receiving the transfer. However, you can preserve the form data and query string of the original page by passing a true value to the optional second argument, of the Server.Transfer() method. The second argument takes a Boolean value that indicates whether to preserve the form and query string collections.

When you set the second argument to true, you need to be aware of one thing: that the destination page contains the form and query string collections that were created by the original page. As a result, the hidden _VIEWSTATE field of the original page is also preserved in the form collection. The view state is page scoped and is valid for a particular page only. This causes the ASP.NET machine authentication check (MAC) to announce that the view state of the new page is tampered with. Therefore, when you choose to preserve the form and query string collections of the original page, you must set the EnableViewStateMac attribute of the Page directive to false for the destination page.

The Server.Execute() Method

The Server.Execute() method allows the current ASPX page to execute a specified ASPX page. The path to the specified ASPX page must be on the same Web server and must not contain a query string.

Bad HTML Code

The output returned to the browser by Server.Execute() and Server.Transfer() might contain multiple <html> and <body> tags because the response stream remains the same while executing another ASPX page. Therefore, the output that results from calling these methods might contain bad HTML code.

After the specified ASPX page is executed, control transfers back to the original page from which the Server.Execute() method was called. This technique of page navigation is analogous to making a method call to an ASPX page.

The called ASPX page has access to the form and query string collections of the calling page: Thus, for the reasons explained in the previous section, you need to set the EnableViewStateMac attribute of the Page directive to false on the called ASPX page.

By default, the output of the executed page is added to the current response stream. This method also has an overloaded version in which the output of the redirected page can be fetched in a TextWriter object instead of adding the output to the response stream. This helps you control where the output is placed on the original page.

STEP BY STEP

3.13 Using the Response.Redirect(), Server.Transfer(), and Server.Execute() Methods

  1. Add a new Web form to the project. Name the Web form StepByStep3_13.aspx. Change the pageLayout property of the DOCUMENT element to FlowLayout.

  2. Add three Label controls, a Literal control (litDynamic), two TextBox controls (txtRows, txtCells), and three Button controls (btnTransfer, btnExecute, and btnRedirect) to the Web form, as shown in Figure 3.12.

  3. Figure 3.12Figure 3.12 The design of a form that allows you to specify rows and columns to create a table dynamically.

  4. Double-click the three Button controls to add an event handler to the Click event of each button. Add the following code in their event handlers:

  5. private void btnRedirect_Click(object sender, 
      System.EventArgs e)
    {
      // Calling Response.Redirect by passing
      // Rows and Cells values as query strings
      Response.Redirect("StepByStep3_13a.aspx?Rows="
        + txtRows.Text + "&Cells=" + txtCells.Text);
    }
    
    private void btnTransfer_Click(object sender, 
      System.EventArgs e)
    {
      // Writing into Response stream
      Response.Write(
        "The following table is generated " +
        "by StepByStep3_13a.aspx page:");
      // Calling the Server.Transfer method
      // with the second argument set to true 
      // to preserve the form and query string data
      Server.Transfer("StepByStep3_13a.aspx", true);
      // Control does not come back here
    }
    
    private void btnExecute_Click(object sender, 
      System.EventArgs e)
    {
      // Creating a StringWriter object
      StringWriter sw = new StringWriter();
      // Calling the Server.Execute method by 
      // passing a StringWriter object
      Server.Execute("StepByStep3_13a.aspx", sw);
      // Control comes back
      // Displaying the output in the StringWriter
      // object in a Literal control
      litDynamic.Text = sw.ToString();
    }
  6. Add a new Web form to the project. Name the Web form StepByStep3_13a.aspx. Change the pageLayout property of the DOCUMENT element to FlowLayout.

  7. Add a Table control (tblDynamic) from the Web Forms tab of the Toolbox to the Web form.

  8. Switch to the HTML view of the StepByStep3_13a.aspx file and modify the Page directive to add the EnableViewStateMac="false" attribute:

  9. <%@ Page language="c#" 
       Codebehind="StepByStep3_13a.aspx.cs" 
       AutoEventWireup="false" 
       Inherits="_315C03.StepByStep3_13a" 
       EnableViewStateMac="false" 
    %>
  10. Switch to code view and add the following method in the class definition:

  11. private void CreateTable(Int32 intRows, Int32 intCells)
    {
      // Create a new table 
      TableRow trRow;
      TableCell tcCell;
    
      // Iterate for the specified number of rows
      for (int intRow=1; intRow <= intRows; intRow ++)
      {
        // Create a row 
        trRow = new TableRow();
        if(intRow % 2 == 0)
        {
          trRow.BackColor = Color.LightBlue;
        }
        // Iterate for the specified number of columns
        for (int intCell=1; intCell <= intCells; 
           intCell++)
        {
          // Create a cell in the current row
          tcCell = new TableCell();
          tcCell.Text = "Cell (" + intRow + "," 
            + intCell + ")";
          trRow.Cells.Add(tcCell);
        }
        // Add the row to the table
        tblDynamic.Rows.Add(trRow);
      }
    }
  12. Add the following code in the Page_Load() event handler:

  13. private void Page_Load(
      object sender, System.EventArgs e)
    {
      if(Request.Form["txtRows"] != null)
      {
        // If the request contains form data then the
        // page is called from the Server.Transfer or 
        // Server.Execute methods from the 
        // StepByStep3_13.aspx page. Get the Rows and 
        // Cells values from the form collection and 
        // Create a table. 
        CreateTable(
          Int32.Parse(Request.Form["txtRows"]),
          Int32.Parse(Request.Form["txtCells"]));
      }
      else if(Request.QueryString["Rows"] != null)
      {
        // If the request contains query string data
        // that means the response is redirected from 
        // the StepByStep3_14.aspx page. Get the Rows
        // and Cells value from the query string and 
        // Create a table.
        Response.Write("StepByStep3_13a.aspx:");
        CreateTable(
          Int32.Parse(Request.QueryString["Rows"]),
          Int32.Parse(Request.QueryString["Cells"]));
      }
    }
  14. Set StepByStep3_13.aspx as the start page in the project.

  15. Run the project. Enter the number of rows and cells and click all three buttons one by one. When you click the Redirect button, the browser is redirected to StepByStep3_13a.aspx by passing the Rows and Cells values as the query string data as shown in Figure 3.13. When you click the Transfer button, the browser doesn't change the page name in the location bar, but the control gets transferred to the StepByStep3_13a.aspx page as shown in Figure 3.14. Finally, when you click the Execute button, the StepByStep3_13a.aspx page is executed and control comes back to the calling page, where the output of the Server.Execute() method is displayed as shown in Figure 3.15.

Figure 3.13Figure 3.13 The Response.Redirect() method can be used to navigate to a URL that contains query strings.

Figure 3.14Figure 3.14 The Server.Transfer() method is used to navigate to an ASPX page on the same server without causing an additional roundtrip.

Figure 3.15Figure 3.15 The Server.Execute() method executes the specified ASPX page and returns the control back to the calling page.

In fact, it's a good idea to keep the second argument set to false when using the Server.Transfer() method. When you want to pass some values from one page to another in the current HTTP request, instead of using the form and query string collections, you should use the HttpContext object. The HttpContext object gives access to all the information about the current HTTP request. It exposes a key-value collection via the Items property in which you can add values that will be available for the life of the current request. The Page class contains a property called Context that provides access to the HttpContext object for the current request.

You can use two techniques to access the values of one page from another page in the current HTTP request using the HttpContext objects—HttpContext.Handler and HttpContext.Items. I have demonstrated these techniques in the Guided Practice Exercise 3.2 and in the Exercise 3.2, respectively.

Guided Practice Exercise 3.2

When using the Server.Transfer() method, for security reasons, you might not want to disable the machine authentication check for the view state of a page or for an application. How would you pass the state of one page to another in that case?

The Page class contains a property called Context that provides access to the HttpContext object for the current request. The Handler property of the HttpContext object provides the instance of the page that first received the HTTP request.

To use the HttpContext.Handler property in your code, you should take the following steps:

  • Expose the control values as public properties in the page that transfers the control.

  • In the target page, create an instance of the previous page's class.

  • Use the HttpContext.Handler property to retrieve the instance of the handler for the previous page. Initialize the object created in the preceding step with this value.

  • Use the instance of the previous page's class to access its properties.

In this exercise, you are required to modify Step by Step 3.13 to use the HttpContext.Handler property to retrieve the properties of the first page in the second page. How would you make this modification?

You should try working through this problem on your own first. If you are stuck, or if you'd like to see one possible solution, follow these steps:

  1. Open the project 315C03. Add a new Web form GuidedPracticeExercise3_2 to the project. Change the pageLayout property of the DOCUMENT element to FlowLayout.

  2. Add three Label controls, two TextBox controls (txtRows, txtCells), and one button control (btnTransfer) on the Web form.

  3. Switch to the code view and add the following property definition in the class definition:

  4. // Declaring properties to expose
    // the number of Rows and Cells entered
    public Int32 Rows
    {
      get
      {
        return Int32.Parse(txtRows.Text);
      }
    }
    public Int32 Cells
    {
      get
      {
        return Int32.Parse(txtCells.Text);
      }
    }
  5. Double-click the Transfer button control and add the following code in the Click event handler:

  6. private void btnTransfer_Click(object sender, 
      System.EventArgs e)
    {
      // Writing into Response
      Response.Write(
        "The following table is generated " +
        "by GuidedPracticeExercise3_2a.aspx page:");
      // Calling the Server.Transfer method
      Server.Transfer("GuidedPracticeExercise3_2a.aspx");
      // Control does not come back here
    }
  7. Add a new Web form to the project. Name the Web form GuidedPracticeExercise3_2a.aspx. Change the pageLayout property of the DOCUMENT element to FlowLayout.

  8. Add a Table control (tblDynamic) from the Web Forms tab of the Toolbox to the Web form.

  9. Switch to code view and add the following code in the class definition to create an instance of the GuidedPracticeExercise3_2 page:

  10. // Declare a variable to store an instance of 
    // the GuidedPracticeExercise3_2 Web form
    public GuidedPracticeExercise3_2 pageExercise3_2;
  11. Add the following code in the Page_Load() event handler:

  12. private void Page_Load(
      object sender, System.EventArgs e)
    {
      if(!IsPostBack)
      {
        // Because its the same request context, 
        // get the reference to the 
        // GuidedPracticeExercise3_2 page
        // through the current request Context.
        // Get the Rows and Cells value from the 
        // GuidedPracticeExercise3_2 Web form's 
        // properties and Create a table.
        pageExercise3_2 = (GuidedPracticeExercise3_2)
          Context.Handler;
        CreateTable(pageExercise3_2.Rows, 
          pageExercise3_2.Cells);
      }
    }
  13. Switch to code view and add the following method in the class definition:

  14. private void CreateTable(Int32 intRows, Int32 intCells)
    {
      // Create a new table 
      TableRow trRow;
      TableCell tcCell;
    
      // Iterate for the specified number of rows
      for (int intRow=1; intRow <= intRows; intRow ++)
      {
        // Create a row 
        trRow = new TableRow();
        if(intRow % 2 == 0)
        {
          trRow.BackColor = Color.LightBlue;
        }
        // Iterate for the specified number of columns
        for (int intCell=1; intCell <= intCells; 
          intCell++)
        {
          // Create a cell in the current row
          tcCell = new TableCell();
          tcCell.Text = "Cell (" + intRow + "," 
            + intCell + ")";
          trRow.Cells.Add(tcCell);
        }
        // Add the row to the table
        tblDynamic.Rows.Add(trRow);
      }
    }
  15. Set GuidedPracticeExercise3_2.aspx as the start page in the project.

  16. Run the project. Enter the number of rows and cells and click the Transfer button. You should see that the browser doesn't changes the page name in the location bar, but the control gets transferred to the GuidedPracticeExercise3_2a.aspx page. The GuidedPracticeExercise3_2a.aspx page is able to access the Rows and Cells properties of the GuidedPracticeExercise3_2.aspx page via the HttpContext.Handler property.

If you have difficulty following this exercise, review the section "Navigation between Pages" earlier in this chapter and perform Step by Step 3.13. After doing this review, try this exercise again.

REVIEW BREAK

  • The Response.Redirect() method can be used to redirect the browser to any specified URL. The specified URL can point to any resource and might also contain query strings. Use of Response.Redirect() method causes an additional roundtrip.

  • The Server.Transfer() method performs a server-side redirection of a page, avoiding extra roundtrip to the server. The Server.Transfer() method can only be used to redirect to an ASPX page residing on the same Web server. The URL to the redirected ASPX page cannot contain query strings, although you can preserve the form and query string collection of the main page to the redirected page by passing the true value to an optional second parameter.

  • The Server.Execute() method is like a method call to an ASPX page. This method executes the specified ASPX page and returns the execution to the calling ASPX page. The page specified as an argument to the Server.Execute() must be an ASPX page residing on the same Web server, and the argument should not contain query string data. The ASPX page to be executed contains access to the form and query string collections of the main page.

  • You should set the EnableViewStateMac attribute of the Page directive to false for the destination page; in case of calling the page via the Server.Execute() method or the Server.Transfer() method with the second argument, set it to true.

Pearson IT Certification Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Pearson IT Certification 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 Pearson IT Certification 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 Adobe Press. 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.pearsonitcertification.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