Chapter 9. Web Applications The McGraw-Hill Companies, Inc. All rights reserved. McGraw-Hill

Transcription

1 Chapter 9 Web Applications McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved.

2 Chapter Objectives - 1 Explain the functions of the server and the client in Web programming Create a Web Form and run it in a browser Describe the differences among the various types of Web controls and the relationship of Web controls to controls used on Windows forms Understand the event structure required for Web programs Design a Web Form using tables McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-2

3 Chapter Objectives - 2 Control the styles used on Web pages using cascading style sheets (CSS) Create multiple pages in a Web application Navigate using the HyperLink control and the Server object Validate Web input using the validator controls Use state management to preserve values in variables Use AJAX to update a portion of a Web page Define ASP.NET, XML, WSDL, and SOAP McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-3

4 C# and Web Programming Web Forms are used to create the user interface for Web applications A Web Form displays as a document in a browser You can create documents that display on mobile devices, such as cell phones and PDAs (using the Standard Edition and above) McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-4

5 Client/Server Web Applications Web applications require a server and a client Server sends the Web Pages to the client Client displays the Web Pages in a browser McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-5

6 Web Servers To develop Web applications Use a remote Web server Make your local machine a Web server Visual Studio Web Server Installs automatically with Visual Web Developer or Visual Studio Simplifies development, testing, and debugging Use IDE tools to transfer application to an IIS Web server after development to share with others Internet Information Services (IIS) McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-6

7 Web Clients Browsers display pages written in a markup language such as HTML or XHTML Pages may also contain program logic Script JavaScript, VBScript, JScript Java applets Programming for a network intranet Users browser is known Programming for the Internet Test and check output on multiple browsers Internet Explorer, Mozilla FireFox and Opera McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-7

8 Web Pages Web pages are stateless The page does not store any information about its contents from one invocation to the next Techniques for working around the stateless limitation Storing cookies on the local machine Sending state information to the server as part of the page's address, called the uniform resource locator (URL) The server can send the state information back with the next version of the page McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-8

9 ASP.NET ASP.NET 3.5 is the latest Web programming technology from Microsoft ASP.NET provides libraries, controls, and programming support for programs that: Interact with the user Maintain state Render controls Display data Generate appropriate HTML Write object-oriented, event-driven Web applications using C# and ASP.NET McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-9

10 C# and ASP.NET Each Web Form has two distinct pieces HTML and instructions needed to render the page C# code A Web Form generates two files:.aspx extension for the HTML.aspx.cs extension for the C# code Holds the logic to respond to events Called the "code behind" file C# code is not compiled into an.exe file, it is compiled into a dynamic link library (dll) file McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-10

11 Types of Web Sites Web applications are referred to as Web sites in VS 2008 Four types of Web sites 1.File System 2.Local IIS 3.FTP site 4.Remote site McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-11

12 File System Web Sites Store Web pages and associated files in any folder on the local computer or on the network Does not expose the computer to security vulnerabilities Does not require administrative rights to create and debug a Web project Runs on Home Edition of Vista or XP McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-12

13 IIS Web Sites IIS on a local computer hosts a Web server that must be secured Requires administrative rights on the computer to create IIS Web projects By default files are stored in C:\inetpub\wwwroot folder A virtual IIS directory can be created to store a Web site McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-13

14 Remote Sites and FTP Sites Administrative rights on the host computer must be granted to do development on a remote Web server FTP cannot be used to create a new Web site A previously created FTP Web site can be opened in Visual Studio McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-14

15 Creating a Web Site Select New Web Site from the File menu In the New Web Site dialog box, select the template, location, and language Give the Web site a name by appending the name to the location McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-15

16 Web Page Files A new Web site automatically contains one Web page, Default.aspx Visual representation of the page (HTML tags) A second file, Default.aspx.cs, holds the C# code for the page ASP.NET has a second model for Web applications single-file model Stores all HTML, control definitions, and code in one single file The textbook teaches the code-separation model that uses two separate files McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-16

17 Web Forms in the Visual Studio IDE Differences between a Web application and a Windows Forms application Web Form (page or document) not a Windows Form Toolbar List of files in the Solution Explorer Toolbox has different controls Properties and events different than controls that have a Windows counterpart Views available in the IDE are Design, Source (HTML or ASP.NET) or a Split window McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-17

18 Viewing the HTML Code Three tabs at bottom of Web Form Design Split Splits the Document window horizontally to see both the design and source Source Static HTML code McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-18

19 Controls - 1 Several types of controls available for Web Forms Standard (ASP.NET server controls) Richest and most powerful controls provided by ASP.NET and.net framework Data Display database data Validation Validate user input before it is sent to server Navigation Includes the Menu control Login Login controls and wizards WebParts Change the appearance and behavior of the interface from the browser McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-19

20 Controls - 2 AJAX Extensions Provide for faster Web page loading and richer interfaces HTML Standard elements that operate only on the client HTML controls pass to and from the server as static text Others Depending on version of VS, other sections may be available (i.e. Reporting) McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-20

21 Controls - 3 In Design view, client-side HTML controls and ASP server controls are different Popup DataTips identify the type of control and its ID (Name) McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-21

22 Event Handling Write C# code for events of Web controls in the same way as for Windows controls Events may occur on either the client or server The process of capturing an event, sending it to the server, and executing the required methods is all done automatically Events of Web Forms and controls are different than for Windows Forms Examples Page.Load versus Form.Load Button control has much shorter list of events for a Web Form versus a Windows From McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-22

23 Files Web application files differ greatly from a Windows application aspx file Holds specifications for the user interface used by the server to render pages aspx.cs file Code-behind file for the aspx file McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-23

24 Debugging The IDE does not automatically generate the code necessary for debugging a Web application Run without Debugging Ctrl + F5 or Debug/Start without debugging McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-24

25 Run with Debugging If you try to run with debugging (F5), a message box gives the choice to run without debugging or add the debugging code to the Web.config file Add the following line of code to the Web.config file to run with debugging <compilation debug = true /> Set breakpoints, single step execution, and display the contents of variables and properties at debugging time Always remove debugging support before deploying an application Debugging code slows an application considerably McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-25

26 Testing in Other Browsers To test in another browser, in the Solution Explorer: Right-click on the project name Select Browse With Select from browsers installed on the computer McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-26

27 Laying Out Web Forms Factors that will affect the layout of page Browsers Screen sizes Screen resolutions ASP.NET generates appropriate HTML to render the page in various browsers but cannot be aware of the screen size, resolution, or window size on the target machine McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-27

28 Using Tables for Layout HTML tables contain rows and columns and allow control over placement of elements on a Web page Add controls and text to the table cells to align the columns A table is an HTML control, which requires no server-side programming McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-28

29 Placing Controls or Text in a Table - 1 Add controls to any table cell or type text in a cell during design time To refer to the text in a cell at run time, add a label and give it an ID or type text directly into the cell Merge cells to allow room for a title or a larger image McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-29

30 Placing Controls or Text in a Table - 2 Table borders show at design time but not at run time McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-30

31 Absolute Positioning Places controls in a specific X and Y position Controls may not show up if user has set browser window to small size Controls may overlap if the user has selected a large font size for the browser window Controls can be dragged using the white tab at the top of a selected control Controls remain in the same position relative to the Web page McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-31

32 Including Images on Web Pages - 1 Use the Image control to add graphics to a Web page Concept is similar to the PictureBox on Windows Forms, but the graphic file is connected differently due to the nature of Web applications Each Image control has an ImageUrl property that specifies the location of the graphic file Best to first copy the graphic into the Web site folder Add an Image control to a cell in a table or directly on a Web page McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-32

33 Including Images on Web Pages - 2 Web page table has three rows and three columns Image and company title are in first row, textbox is in second row, hyperlink is in last row McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-33

34 Cascading Style Sheets New tools for using styles in Web applications are called Expression Web Expands, enhances and simplifies using cascading style sheets (CSS) Use CSS to create, modify and apply styles to single elements on a page, an entire page, all pages, or all applications of an organization McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-34

35 Using Styles - 1 Styles are rules that specify page layout, position, font, color, alignment, margins, borders, background and bullet and numbering formats Create and apply new styles within a page Attach an external.css file to apply styles Save styles to an external.css file for use on other pages or Web sites McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-35

36 Using Styles - 2 Styles can be defined in several locations Web page inline style For elements that appear only once on a page style section page style For elements that may be used in more than one location on a page external style sheet -.css file For elements that may appear on more than one page or in multiple Web sites McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-36

37 Using Styles - 3 Cascading refers to the order of precedence of the style rules For example Style sheet (global) sets font, color, size, alignment Local (page-defined) style for the color and size takes precedence (font and alignment still in effect from style sheet) Inline (more local) style for the size takes precedence over local and style sheet (color from local and font and alignment from style sheet remain) McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-37

38 Types of Styles - 1 Several new tools are available to define, apply, modify and change the location of styles Apply Styles window Manage Styles window Use the icons in the CSS Style Types table to identify the various types of styles McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-38

39 Types of Styles - 2 McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-39

40 New Style Tools New windows to define, apply and manage styles CSS Properties Manage Styles Apply Styles New Style Application toolbar appears in the default layout of the IDE McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-40

41 New Style Windows and Style Application Toolbar McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-41

42 The Style Application Toolbar Select Manual or Auto style application Auto allows software to determine where to place CSS code Manual allows choice of location of the styles using the Target Rule drop-down list New Inline Style places style code into HTML code Apply New Style allows creation of a new style in a new or existing.css file McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-42

43 Defining Styles Define a new style in the New Style dialog box Choose the category and make settings For example Font Block Text-align, text-indent, vertical align List Bullet and numbering attributes Table Borders and spacing McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-43

44 Managing Styles In the Manage Styles Window, preview each style Drag styles from one category to another to change the location of the style definition A style created in the current page can be moved to a.css file to allow its use in other pages In the CSS Properties window see the settings for a given style McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-44

45 Applying Styles Apply styles from several locations Apply Styles window Select the element on the page and click the desired style Manage Styles window Select the element on the page, right-click the desired style name and select Apply Style from the context menu New Style dialog box Check the box for Apply new style to document selection McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-45

46 Modifying Styles Change attributes of a style from the Apply Styles or Manage Styles window Right-click on style name, select Modify Style from the context menu Modify style attributes in the CSS Properties window McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-46

47 Navigating Web Pages ASP.NET provides several techniques to navigate from one Web page to another Easiest form of navigation is to use a HyperLink control McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-47

48 Using Hyperlinks Add a HyperLink control to allow the user to navigate to another page or another site Set properties of the HyperLink control Text Text to display for the user NavigateUrl Specify the URL to which to navigate For another Web site, type the Web address (URL) For another page in the application, use the Select URL dialog box and select the page from a list McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-48

49 Adding a Second Web Page Add a new form to the project Add controls to the new page Add a HyperLink to the Main Page Set the Start Page Run the application, test the links McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-49

50 Transferring Pages in Code At times a hyperlink cannot be used because some other action in code needs to be performed prior to the transfer Transfer to another page in code Use the Server.Transfer method Server.Transfer ( Offer.aspx ); McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-50

51 Using the Validator Controls - 1 ASP.NET provides several validator controls that can automatically validate input Add a validator control Attach it to an input control (such as a text box) Set the error message to display At run time, when the user inputs data, the error message displays if the validation rule is violated Validator controls run on the client-side McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-51

52 Using the Validator Controls - 2 A blank entry passes the validation for each of the controls except the RequiredFieldValidator To ensure a field is not blank and it passes a range check attach both a RangeValidator and a RequiredFieldValidator to the field Enter a complete message in the ErrorMessage property or set the property to an asterisk McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-52

53 Using the Validator Controls - 3 Validator Controls RequiredFieldValidator CompareValidator RangeValidator RegularExpressionValidator ValidationSummary Requires that the user enter something into the field Compares the value in the field to the value in another control or to a constant. Also can be used to verify that the input value can be converted to the correct data type Requires that the input value falls in the specified range Validates against a regular expression, similar to the mask in a masked text box Displays a summary of all of the messages from the validator controls McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-53

54 Maintaining State Web pages hold static data Each time a page is displayed or redisplayed it is a fresh copy Each time the page is posted back to the server a new copy of the program is loaded Steps must be taken to maintain the state of the page Otherwise the values of variables and controls on the page will be lost in every postback McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-54

55 Retaining the Contents of Controls ASP.NET can retain and redisplay control contents Web controls have an EnableViewState property Set to true by default Indicates to the server to send the control s contents back with the page McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-55

56 Retaining the Values of Variables - 1 Local variables work the same in a Web or Windows application Class-level variables are lost unless steps are taken to save them Store the value of a class-level variable in a control on a Web page EnableViewState property holds the value during postback McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-56

57 Retaining the Values of Variables - 2 Set up a control with its Visible property set to false or use the HiddenField control Assign the class-level variable to the invisible control For a hidden field, use the (string) Value property // Declare a class level variable. private decimal discounttotaldecimal; protected void submitbutton_click(object sender, EventArgs e) { //... Calculations omitted. discounthiddenfield.value = discounttotaldecimal.tostring(); } McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-57

58 Checking for Postback The Page_Load event occurs many times (during each postback) in a Web application IsPostBack property is set to false for an initial page load and true for all page loads following the first Test for IsPostBack == false to perform initialization tasks Test for IsPostBack == true to perform tasks only on postback McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-58

59 Passing Values to a Second Page A HiddenField control maintains the value of a class-level variable for a single page Send information to a second page Use the Session variable technique to pass data between pages McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-59

60 Using a Session Variable - 1 One instance of the Session object exists for each user of an application Use to store information about the user on the server Each time a user accesses an application, a Session object is created with a unique SessionID Session values are maintained as long as the session exists Sessions can time out, terminate or users can logout McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-60

61 Using a Session Variable - 2 Drawbacks to session objects Information is stored on server Large amounts of data for multiple users can bog down the server Web sites split server loads among several systems (Web Farm) State information might be on a different server than where the postback originates.net handles this problem by specifying the name of the machine that stores the session values in the Web.config file McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-61

62 Using a Session Variable - 3 Use the Contents collection of the Session object to store values in code Each item in the collection is a key/value pair Make up a name (the key) and assign a value Clear all session variables by using the Session.Clear method McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-62

63 AJAX -1 Create interactive Web applications with Asynchronous JavaScript and XML (AJAX) AJAX allows reloading of only a portion of a Web page on each postback Only the portion of a page that changes is downloaded and rendered Dramatically increases loading speed AJAX is an open and cross-platform technology McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-63

64 AJAX - 2 AJAX pages must include a ScriptManager component (in the toolbox under AJAX Extensions) Add other controls such as the UpdatePanel A container for other controls Placing controls inside an UpdatePanel determines which portion of the page updates on a postback The area outside the UpdatePanel remains unchanged McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-64

65 Managing Web Projects Moving and renaming Web projects is easy when using File System Web sites, as opposed to IIS sites Make sure the project is closed Move, rename, or copy the project folder To open the moved or renamed project, first open the IDE and select File/Open Web Site and navigate to the project s folder McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-65

66 Using the Copy Web Site Tool Copy an entire Web site from one location to another on the same computer, to another computer on a network, or to a remote site Copy the Web site to a remote server where it can be accessed by multiple users Select Website/Copy Web Site to begin the operation McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-66

67 Some Web Acronyms - 1 XML Extensible Markup Language. This popular tag-based notation is used to define data and their format and transmit the data over the Web. XML is entirely text based, does not follow any one manufacturer s specifications, and can pass through firewalls. SOAP Simple Object Access Protocol. An XML-based protocol for exchanging component information among distributed systems of many different types. Since it is based on XML, its messages can pass through network firewalls. McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-67

68 Some Web Acronyms - 2 HTTP HyperText Transfer Protocol. The protocol used to send and receive Web pages over the Internet using standardized request and response messages. Web Service Code in classes used to provide middle-tier services over the Internet. WSDL Web Services Description Language. An XML document using specific syntax that defines how a Web service behaves and how clients interact with the service. McGraw-Hill 2010 The McGraw-Hill Companies, Inc. All rights reserved. 9-68