1. Introduction to ASP.NET

2. Static and Dynamic Web Applications
HTML is used to create static content
Browser software interprets HTML tags and formats the output
Dynamic Web applications enable the user to interact with the Web application
Examples of dynamic Web applications include shopping carts, membership databases, online catalogues, and personalized web sites

3. Server-side Programming
Server-side programs allowed you to create dynamic Web applications such as process a form or manage a database
The Web server sends static HTML to the client’s browser
Because the processing of the script occurs on the server, you can hide code from the client
Microsoft’s implementation of Web server programming technology is referred to as Active Server Pages (ASP)
Server-side scripts can be used to create dynamic Web applications that are browser independent

4. Processing Web Pages with ASP

5. ASP.NET The latest version of ASP is known as ASP.NET
Visual Studio .NET is a developer application used to create ASP.NET Web applications
There are two main types of Web resources created with ASP.NET applications
WebForms are ASP.NET pages within an ASP.NET application
Web Services are ASP.NET Web pages that contain publicly exposed code so that other applications can interact with them
Web Services are identified with the file extension .asmx

6. WebForms The ASP.NET WebForm is separated into two logical areas:
The HTML template
A collection of code behind the WebForm
Contains the design layout, content, and the controls
Creates the user interface, or presentation layer
Instructs the browser how to format the Web page
Is created using a combination of HTML controls, HTML Server controls, Mobile Controls, and ASP.NET controls

7. Server Controls
HTML Server controls are similar to the HTML controls, except they are processed by the server
Add runat = "server" to the HTML control to transform it into an HTML Server control
HTML control: <input type="text">
HTML Server control:
<input type="text" runat="server"/>
<input type=”radio” runat=”server” value=”Yes”/> Yes
Server-side programs can interact with the control before it is rendered as a plain HTML control and sent to the browser

8. XHTML
XHTML requires that all HTML elements be compliant with XML standards
XML is another example of a markup language that can be used to build applications
One of the rules of XML is that all controls must have a closing tag, or end with />. So, all controls that do not have a closing tag are closed in the initial tag with />
The XML, HTML, and XHTML standards are maintained by the World Wide Web Consortium (

9. ASP.NET Controls ASP.NET form controls will create the HTML code
ASP.NET Server controls are organized as:
ASP.NET Form Controls
Data Validation Controls
User Controls
Mobile Controls
ASP.NET controls are usually identified with the prefix asp: followed by the name of the control
ASP.NET button:
<asp:Button id="ShowBtn" runat="server" Text="Show the message." />

10. HTML Server Versus ASP.NET Server Controls
ASP.NET form controls can interact with client-side events such as when the user clicks on a button
When the event occurs, ASP.NET can trigger a script to run on the server
ASP.NET form controls also have different properties than their HTML server control counterparts
HTML Server label control
Message1.InnerHTML = "Product 1"
ASP server label control
Message2.Text = "Product 2"

11. Browser Source Code
It is very important that you look at the browser’s source code of each ASP.NET page that you create in order to understand what the Web server is sending to the browser
ASP.NET code is never sent to the browser
Only HTML tags, along with client-side scripts, are sent to the browser
Many errors are related to the syntax of the HTML that is sent to the browser, such as a missing closing tag, or a missing quotation mark
By viewing the source code in the browser, you can more quickly locate the HTML syntax errors

12. User Controls
User controls are external files that can be included within another WebForm
User controls allow you to reuse code across multiple files
For example, you can create a user control that displays the top ten music selections for the week
You can use this control on the home page; they are often used for creating self-contained code, headers, menus, and footers
User controls replace the functionality of ASP server-side include pages
They are identified with the file extension .asmx

13. Other ASP.NET Server Controls
Data validation controls
A series of controls that validate form data without extensive JavaScript programming
Mobile controls
A series of controls that provide form functionality within wireless and mobile devices
Literal controls
Page content that is not assigned to a specific HTML control such as a combination of HTML tags and text to the browser

14. Server Controls within Visual Studio .NET
In Visual Studio .NET most of the ASP.NET Server controls are located on the Web Forms tab in the toolbox
Figure 1-2 Server controls with Visual Studio.NET

15. The Code Behind the Page
Server programs are written in a separate file known as the code behind the page
By separating the programming logic and presentation layer, the application becomes easier to maintain
Only Server controls can interact with the code behind the page
Written in any ASP.NET compatible language such as Visual Basic .NET, C#, Perl, or Java
Filename is the same as the WebForm filename
Add a file extension that identifies the language
Visual Basic .NET use .vb (mypage.aspx.vb)
C# use .cs (mypage.aspx.cs)

16. Code Behind the Page
The location of the code behind the page is determined via a property that is set on the first line in the page using directive
Page Language="vb" Codebehind="WebForm1.vb" Inherits="TaraStore.WebForm1"%>
directive allows you to set the default properties for the entire page such as the default language
The CodeBehind property identifies the path and filename of the code behind the page
The Inherits property indicates that the code behind the page inherits the page class
This page class contains the compiled code for the entire page

17. Compiling the Page Class
The compiled code behind the page is the class definition for the page
A class is a named logical grouping of code
The class definition contains the functions, methods, and properties that belong to that class
In Visual Studio .NET the process of compiling a class is called building
When you build the application, you compile the code into an executable file
Visual Studio .NET compiles the code behind the page into an executable file and places the file in the bin directory

18. Compiling the Page Class
Figure 1-3 Compiling the ASP.NET page and the code behind the page into the Page class

19. Postback
To keep this information across browser requests is known as maintaining state
The process of posting data back to a form is known as postback
All server controls support postback by default
A hidden form field named _ViewState is a very long encoded string that contains information required to maintain the form data across multiple page requests
This encoded string is decoded by the Web Server and will change each time the form is reposted back to the server
The values that are stored with the page remain with the page

20. Postback Data Using the _ViewState Hidden Field
Figure 1-4 Postback data using the _ViewState hidden field

21. Enable _ViewState Property
The Web page does not have to support the postback feature
You can turn the postback property on or off by setting the EnableViewState property to true or false within directive
You can also turn the EnableViewState property on or off by setting the property for any individual server control, or for the entire application by setting the property in the application configuration files
In the following sample code, the postback property is turned off for the entire page for all server controls. This code is placed on the first line in the ASP.NET page
Page EnableViewState="false" %>

22. Page Class Events
The Page Class consists of a variety of methods, functions, and properties that can be accessed within the code behind the page
The first time a page is requested by a client, a series of page events occurs
The first page event is the Page_Init event which initializes the page control hierarchy
The Page_Load event loads any server controls into memory and occurs every time the page is executed

23. Page Class Event Cycle
Figure 1-5 Page class event cycle

24. Procedures
In the following sample code, a message is displayed when the Page_Load event occurs
In Visual Basic .NET, the event handler is known as a procedure
When you create a procedure, you must identify the beginning of the procedure with the keyword Sub, and the ending with the keywords End Sub
Sub Page_Load(s As Object, e As EventArgs)
Message.InnerHtml = "Welcome!"
End Sub

25. Control Events
Control events can be action events, such as the click event for a server button control, or change events, such as when the value of a server text control changes
If a user clicks a server button control, then you can execute code in the OnServerClick event handler
The HTML server button control named MyBtn and a span tag named Message
<button id="MyBtn" runat="server" OnServerClick="MyBtn_Click">
Click me!</button>
<h1><span id="Message" runat=server /></h1>

26. Control Events
When the user clicks the button, an OnServerClick event handler is called
The event handler calls a procedure named MyBtn_Click
In the code behind the page, the OnServerClick event handler can send a message back to the browser
Sub MyBtn_Click(s As Object, E as EventArgs)
Message.InnerHtml = "You clicked me!"
End Sub

27. Trace Property
To view the order in which the server controls are rendered to the Web page, turn on the trace property
The trace feature provides you with the ability to view the page controls, the order in which they are loaded, and the time it takes to load the control
The ID is a property that is assigned to the server control in the Web page
If no ID is provided for the server control, a generic ID value is assigned
To turn on the trace feature, on the first line of code set the trace property for the page to true as shown in the sample code below
Trace = "true" %>

28. Page_UnLoad
When the page unloads, the Page_UnLoad event occurs and the page is removed from the server’s memory
You can use the Page_Unload event handler to close database connections, close files, and release any programming variables or objects
In the sample code below, a message is displayed on the Web page when the page is unloaded
Sub Page_UnLoad(s As Object, e As EventArgs)
Message.InnerHtml = "Goodbye!"
End Sub

29. Built-in ASP.NET Objects
ASP.NET pages have access to objects that are built-in the Web Server, along with their properties and methods
HTTPRequest — object is mapped directly to the Request property of the Page object
HTTPResponse —Used to send information from the Web server to the client’s browser and is used to redirect the user to another Web page. The HTTPResponse object is mapped directly to the Response property of the Page object
Session —Used to share information between a single client and the Web server. The session object is used to store data during the course of a session. The session ends, and the session variable no longer exists when the user closes the browser or when the default session timeout is reached
Application —Allows developers to treat a sequence of Web pages as a single application, which means that information, such as the name of the application or the total number of visitors on the Web site, can be shared among all the users of an ASP application

30. The ASP.NET Page.Request Property
When a browser sends a request for a Web page, the Web server receives the request and some additional information in the TCP/IP header
The TCP/IP header is a portion of the data packet that includes information that determines how to send the file and where to send the file
The TCP/IP header includes the date and time, the type of request (get or post), the page requested, and the HTTP version

31. The ASP.NET Page.Request Property
Additional information includes the default language, the referring page, the IP address of the client, the cookies associated with that domain, and the user agent
The user agent can be used to identify the client software
Because the Request property belongs to the Page class, you can refer to the Request property using Page.Request.PropertyName or Request.PropertyName

32. The ASP.NET Page.Request Property
In the sample code below, three server variables are written to the browser
Server variables are variables that are passed in the TCP/IP header
Response.write(Request.PhysicalPath)
Response.write(Request.UserHostAddress)
Response.Write(Request.UrlReferrer.Host)

33. Browser Object
The user agent provides a string which can be used to detect the browser version
However, the string must be parsed to locate the browser application name and version
With the browser property, you can directly access the browser application name and version without the user agent
The Browser property displays the client browser version, then writes out the short name of the browser application, the version number, and the platform
Response.Write(Request.Browser.Browser)
Response.Write(Request.Browser.Version)
Response.Write(Request.Browser.Platform)

34. Processing a Form Using the QueryString Collection
The Request property provides you access to the form field names and values
If the form method is GET, then the form is sent appended to the URL requested as a single string called the QueryString
If the form method is POST, it is sent as part of the HTTP request body
The Request property contains a Form collection and QueryString collection that allow you to collect form information from both methods

35. Processing a Form Using the Form Collection
The sample code below creates a text box named password and a button named MyBtn
<span id="Message" runat="server">
Please enter your password</span>
<input id="PWD" type="password"
size="8" runat="server"><br/>
<input id="MyBtn" type="submit" value="Login" OnServerClick="MyBtn_Click" runat="server">
The page uses the Request property to retrieve information from the form field and displays the value
Response.write(Request.Form("PWD"))

36. Direct Access to Form Values
A simpler method to retrieve the value from a form field is to directly access the value properties of the form field
The property name (ID) that you use to access the value is different with each type of server control
You can create en event handler that will process the form
Sub MyBtn_Click(s As Object, e As EventArgs)
If (PWD.Value = "Course") Then
Message.InnerHtml = "Welcome!"
Else
Message.InnerHtml = "Try again!"
End If
End Sub

37. Using Page.Request to Retrieve Form Values and Server Variables
Figure 1-8 Using Page.Request to retrieve form values and server variables

38. The ASP.NET Page.Response Property
The Response object is used to send information to the browser
Some of this information identifies the server and server properties
For example, the IP address of the server, and the name and version number of the Web server software are sent to the client
The Cookies collection is used to send cookies to the browser
A status code is sent to indicate whether the browser request was successful or encountered an error

39. Response.Write and Response.WriteFile
The Response object has several methods, such as Write and WriteFile
Write is a a method that allows you to send a string to the browser
You can send text, HTML and client-script to the browser using the write method
WriteFile allows you to send the entire contents of a text file to the Web page
Response.Write("TaraStore<br/>")
Dim strMessage as String = "TaraStore<br/>")
Response.WriteFile(strMessage)
Response.WriteFile("c:\foo.txt")

40. Server-side Redirection
The Response object sends data either via the HTTPResponse object or via the Page.Response property
The Response object holds the contents of the page in an area of memory called the buffer until you send the page
The methods and properties of the Response object allow you to control the caching of content from the ASP page
When the page is processed, a copy of the page created is stored on the server. This copy of the page is known as a cached page
The Response object allows you to redirect the browser to another page. Because this redirection occurs on the server, the visitors never know that they have been redirected to a new page
Response.Redirect("

41. Locating Your ASP.NET Application
You can only view ASP.NET Web pages on a Web Server that supports ASP.NET
The default directory for the root Web site is at C:\InetPub\wwwroot
The root Web site is mapped as localhost as
Web applications in Visual Studio .NET are in a folder in the root directory, named after your application
To deploy a Web application, you copy all of the Web application files to a live Web server on the Internet

42. Web Services
If your business partner is Course Technology and you want to query that company’s product catalog from your Web site, you could:
Post a link
Scrape a Web site (use a program to view a Web site and capture the source code)
Provide a Web Service to their catalog application
Web Services are used to create business-to-business applications
Web Services allow you to expose part or all of your programs over the Internet. The Web Service source file has the extension .asmx
A public registry known as UDDI contains registered public Web Services. Third party Web Services are available at

43. The Tara Store Web Service
Figure 1-9 The Tara Store Web Service

44. The .NET Framework
ASP.NET is used to develop dynamic Web applications within the .NET Framework
The .NET Framework consists of:
A Common Language Runtime (CLR)
A hierarchical set of Base Class Libraries (BCL)
The .NET Framework is the architectural model for creating programs that interface with the operating system and the base class libraries

45. The .NET Framework
Figure The .NET Framework

46. The Base Class Libraries
The base class libraries are commonly used code providing general functions that can be accessed from any application
Libraries contain fundamental code structures and methods that allow you to communicate with the operating system software and other applications
By storing commonly used code in libraries, the code can be reused across applications
The actual library of code is located in one or more dynamic link library files
For example, the code for accessing a database object is stored in the Database class library, located in the file called System.Data.dll

47. Namespace
The base class libraries are organized into logical groupings of code called namespaces
A namespace is a hierarchical way to identify resources in .NET
The System object is at the top of the namespace hierarchy, and all objects inherit from it
ASP.NET: System.Web namespace
WebForms: System.Web.UI namespace
HTML Server Controls: System.Web.UI.Control.HTMLControl
ASP.NET Server Controls: System.Web.UI.Control.WebControl

48. Importing Namespaces
Visual Studio .NET adds references to your projects’ commonly used namespaces by default
You can import the namespaces into your page using directive
The following is the syntax for importing a .NET namespace
Import NamespaceName %>
Below is a sample of how you would import the ASP.NET Page class
Imports System.Web.UI.Page %>

49. Common Language Runtime
Visual Studio .NET and the Common Language Runtime are language independent
Language independence is achieved via the use of the Common Language Runtime (CLR)
The CLR supports new features such as a Common Type System (CTS), Garbage Collection (GC), and an Intermediate Language (IL)
The Common Type System (CTS) requires that all applications built within .NET, including ASP.NET applications, support the same basic data types
Examples of data types are strings and integers
These common data types are derived from the System namespace

50. Common Language Runtime
The compiled code is transformed into an intermediate language called the Microsoft Intermediate Language (MSIL or IL)
An integer in Visual Basic .NET or an int in C# are converted to the same .NET data type, which is Int32
The IL that is created is the same for all languages
The assembly is the compiled .NET program
The assembly contains the IL along with additional information called metadata
Metadata contains information about the assembly
Use the IL Disassembler (ildasm.exe) to view the IL within an assembly

51. Viewing the Assembly
Create a simple class, compile the class into an assembly, then view the class using the IL Disassembler
Open Notepad and type the code shown:
' hello.vb - displays hello world
' Created 06/01/2002
Imports System
Public Module Hello
Sub Main()
Dim s1 As String = "1 - Hello World"
Console.WriteLine(s1)
End Sub
End Module
' Run this at the command line
' vbc hello.vb

52. Compiling a Program
Save the file as "hello.vb" in your c:\Inetpub\wwwroot directory
Open the .NET Command Prompt
Change to your c:\Inetpub\wwwroot using the cd c:\Inetpub\wwwroot command
Type vbc hello.vb and press Enter key. This compiles your program into an executable file named hello.exe in the same folder
Type hello at the command prompt and hit the Enter Key. The program runs and displays the hello world string
Type ILDASM hello.exe. View the compiled assembly using the IL Disassembler

53. Using the ILDASM to View the Assembly and Classes
Figure Using the ILDASM to view the assembly and classes

54. Garbage Collection
Programs that don’t release references to objects cause memory leaks
Memory leaks occur when memory is no longer being used by the application, but cannot be reassigned to another object
In .NET, the Common Language Runtime uses the garbage collector to manage memory
The Garbage Collection (GC) process is the process of allocating and managing the reserved memory
Because of the garbage collection process, .NET applications have fewer problems with memory leaks and circular references than current Windows applications