What You Should Already Know
Before you continue you should have a basic understanding of the following:
- WWW, HTML, XML and the basics of building Web pages
- Scripting languages like JavaScript or VBScript
- The basics of server side scripting like ASP or PHP
ASP.NET is NOT ASP
ASP.NET is the next generation ASP, but it's not an upgraded version of ASP.
ASP.NET is an entirely new technology for server-side scripting. It was written from the ground up and is not backward compatible with classic ASP.
You can read more about the differences between ASP and ASP.NET in the next chapter of this tutorial.
ASP.NET is the major part of the Microsoft's .NET Framework.
What is ASP.NET?
ASP.NET is a server side scripting technology that enables scripts (embedded in web pages) to be executed by an Internet server.
- ASP.NET is a Microsoft Technology
- ASP stands for Active Server Pages
- ASP.NET is a program that runs inside IIS
- IIS (Internet Information Services) is Microsoft's Internet server
- IIS comes as a free component with Windows servers
- IIS is also a part of Windows 2000 and XP Professional
What is an ASP.NET File?
- An ASP.NET file is just the same as an HTML file
- An ASP.NET file can contain HTML, XML, and scripts
- Scripts in an ASP.NET file are executed on the server
- An ASP.NET file has the file extension ".aspx"
How Does ASP.NET Work?
- When a browser requests an HTML file, the server returns the file
- When a browser requests an ASP.NET file, IIS passes the request to the ASP.NET engine on the server
- The ASP.NET engine reads the file, line by line, and executes the scripts in the file
- Finally, the ASP.NET file is returned to the browser as plain HTML
What is ASP+?
ASP+ is the same as ASP.NET.
ASP+ is just an early name used by Microsoft when they developed ASP.NET.
The Microsoft .NET Framework
The .NET Framework is the infrastructure for the Microsoft .NET platform.
The .NET Framework is an environment for building, deploying, and running Web applications and Web Services.
Microsoft's first server technology ASP (Active Server Pages), was a powerful and flexible "programming language". But it was too code oriented. It was not an application framework and not an enterprise development tool.
The Microsoft .NET Framework was developed to solve this problem.
.NET Frameworks keywords:
- Easier and quicker programming
- Reduced amount of code
- Declarative programming model
- Richer server control hierarchy with events
- Larger class library
- Better support for development tools
The .NET Framework consists of 3 main parts:
Programming languages:
- C# (Pronounced C sharp)
- Visual Basic (VB .NET)
- J# (Pronounced J sharp)
Server technologies and client technologies:
- ASP .NET (Active Server Pages)
- Windows Forms (Windows desktop solutions)
- Compact Framework (PDA / Mobile solutions)
Development environments:
- Visual Studio .NET (VS .NET)
- Visual Web Developer
This tutorial is about ASP.NET.
ASP.NET 2.0
ASP.NET 2.0 improves upon ASP.NET by adding support for several new features.
You can read more about the differences between ASP.NET 2.0 and ASP.NET in the next chapter of this tutorial.
ASP.NET 3.0
ASP.NET 3.0 is not a new version of ASP.NET. It's just the name for a new ASP.NET 2.0 framework library with support for Windows Presentation Foundation, Windows Communication Foundation, Windows Workflow Foundation; and Windows CardSpace.
New in ASP.NET
- Better language support
- Programmable controls
- Event-driven programming
- XML-based components
- User authentication, with accounts and roles
- Higher scalability
- Increased performance - Compiled code
- Easier configuration and deployment
- Not fully ASP compatible
Language Support
ASP.NET uses ADO.NET.
ASP.NET supports full Visual Basic, not VBScript.
ASP.NET supports C# (C sharp) and C++.
ASP.NET supports JScript.
ASP.NET Controls
ASP.NET contains a large set of HTML controls. Almost all HTML elements on a page can be defined as ASP.NET control objects that can be controlled by scripts.
ASP.NET also contains a new set of object-oriented input controls, like programmable list-boxes and validation controls.
A new data grid control supports sorting, data paging, and everything you can expect from a dataset control.
Event Aware Controls
All ASP.NET objects on a Web page can expose events that can be processed by ASP.NET code.
Load, Click and Change events handled by code makes coding much simpler and much better organized.
ASP.NET Components
ASP.NET components are heavily based on XML. Like the new AD Rotator, that uses XML to store advertisement information and configuration.
User Authentication
ASP.NET supports form-based user authentication, cookie management, and automatic redirecting of unauthorized logins.
User Accounts and Roles
ASP.NET allows user accounts and roles, to give each user (with a given role) access to different server code and executables.
High Scalability
Much has been done with ASP.NET to provide greater scalability.
Server-to-server communication has been greatly enhanced, making it possible to scale an application over several servers. One example of this is the ability to run XML parsers, XSL transformations and even resource hungry session objects on other servers.
Compiled Code
The first request for an ASP.NET page on the server will compile the ASP.NET code and keep a cached copy in memory. The result of this is greatly increased performance.
Easy Configuration
Configuration of ASP.NET is done with plain text files.
Configuration files can be uploaded or changed while the application is running. No need to restart the server. No more metabase or registry puzzle.
Easy Deployment
No more server-restart to deploy or replace compiled code. ASP.NET simply redirects all new requests to the new code.
Compatibility
ASP.NET is not fully compatible with earlier versions of ASP, so most of the old ASP code will need some changes to run under ASP.NET.
To overcome this problem, ASP.NET uses a new file extension ".aspx". This will make ASP.NET applications able to run side by side with standard ASP applications on the same server.
What You Need
If you have a Beta version of ASP.NET installed, we recommend that you completely uninstall it!
Or even better: start with a fresh Windows 2000 or XP installation!
Windows 2000 or XP
If you are serious about developing ASP.NET applications you should install Windows 2000 Professional or Windows XP Professional.
In both cases, install the Internet Information Services (IIS) from the Add/Remove Windows components dialog.
Service Packs and Updates
Before ASP.NET can be installed on your computer, all relevant service packs and security updates must be installed.
The easiest way to do this is to activate your Windows Internet Update. When you access the Windows Update page, you will be instructed to install the latest service packs and all critical security updates. For Windows 2000, make sure you install Service Pack 2. You should also install the latest version of Internet Explorer.
Tip: Read the note about connection speed and download time at the bottom of this page.
Install .NET
From your Windows Update you can now select the Microsoft .NET Framework.
After download, the .NET framework will install itself on your computer - there are no options to select for installation.
You are now ready to develop your first ASP.NET application!
The .NET Software Development Kit
If you have the necessary bandwidth, you might consider downloading the full Microsoft .NET Software Development Kit (SDK).
We fully recommend getting the SDK for learning more about .NET, and for the documentation, samples, and tools included.
Connection Speed and Download Time
If you have a slow Internet connection, you might have problems downloading large files like the Windows 2000 Service Pack 2 and the Microsoft .NET Framework.
If download speed is a problem, our best suggestion is to get the latest files from someone else, from a colleague, from a friend, or from one of the CDs that comes with many popular computer magazines.
This code displays the example as an HTML page:
| <html> <body bgcolor="yellow"> <center> <h2>Hello Anil !</h2> </center> </body> </html> |
If you want to try it yourself, save the code in a file called "firstpage.htm", and create a link to the file like this:firstpage.htm
Hello W3Schools in ASP.NET
The simplest way to convert an HTML page into an ASP.NET page is to copy the HTML file to a new file with an .aspx extension.
This code displays our example as an ASP.NET page:
| <html> <body bgcolor="yellow"> <center> <h2>Hello Anil!</h2> </center> </body> </html> |
If you want to try it yourself, save the code in a file called "firstpage.aspx", and create a link to the file like this:firstpage.aspx
How Does it Work?
Fundamentally an ASP.NET page is just the same as an HTML page.
An HTML page has the extension .htm. If a browser requests an HTML page from the server, the server sends the page to the browser without any modifications.
An ASP.NET page has the extension .aspx. If a browser requests an ASP.NET page, the server processes any executable code in the page, before the result is sent back to the browser.
The ASP.NET page above does not contain any executable code, so nothing is executed. In the next examples we will add some executable code to the page to demonstrate the difference between static HTML pages and dynamic ASP pages.
Classic ASP
Active Server Pages (ASP) has been around for several years. With ASP, executable code can be placed inside HTML pages.
Previous versions of ASP (before ASP .NET) are often called Classic ASP.
ASP.NET is not fully compatible with Classic ASP, but most Classic ASP pages will work fine as ASP.NET pages, with only minor changes.
Dynamic Page in Classic ASP
To demonstrate how ASP can display pages with dynamic content, we have added some executable code (in red) to the previous example:
| <html> <body bgcolor="yellow"> <center> <h2>Hello W3Schools!</h2> <p><%Response.Write(now())%></p> </center> </body> </html> |
The code inside the <% --%> tags is executed on the server.
Response.Write is ASP code for writing something to the HTML output stream.
Now() is a function returning the servers current date and time.
If you want to try it yourself, save the code in a file called "dynpage.asp", and create a link to the file like this: dynpage.asp
Dynamic Page in ASP .NET
This following code displays our example as an ASP.NET page:
| <html> <body bgcolor="yellow"> <center> <h2>Hello W3Schools!</h2> <p><%Response.Write(now())%></p> </center> </body> </html> |
If you want to try it yourself, save the code in a file called "dynpage.aspx", and create a link to the file like this: dynpage.aspx
ASP.NET vs Classic ASP
The previous examples didn't demonstrate any differences between ASP.NET and Classic ASP.
As you can see from the two latest examples there are no differences between the two ASP and ASP.NET pages.
In the next chapters you will see how server controls make ASP.NET more powerful than Classic ASP.
Limitations in Classic ASP
The listing below was copied from the previous chapter:
| <html> <body bgcolor="yellow"> <center> <h2>Hello W3Schools!</h2> <p><%Response.Write(now())%></p> </center> </body> </html> |
The code above illustrates a limitation in Classic ASP: The code block has to be placed where you want the output to appear.
With Classic ASP it is impossible to separate executable code from the HTML itself. This makes the page difficult to read, and difficult to maintain.
ASP.NET - Server Controls
ASP.NET has solved the "spaghetti-code" problem described above with server controls.
Server controls are tags that are understood by the server.
There are three kinds of server controls:
- HTML Server Controls - Traditional HTML tags
- Web Server Controls - New ASP.NET tags
- Validation Server Controls - For input validation
ASP.NET - HTML Server Controls
HTML server controls are HTML tags understood by the server.
HTML elements in ASP.NET files are, by default, treated as text. To make these elements programmable, add a runat="server" attribute to the HTML element. This attribute indicates that the element should be treated as a server control. The id attribute is added to identify the server control. The id reference can be used to manipulate the server control at run time.
Note: All HTML server controls must be within a <form> tag with the runat="server" attribute. The runat="server" attribute indicates that the form should be processed on the server. It also indicates that the enclosed controls can be accessed by server scripts.
In the following example we declare an HtmlAnchor server control in an .aspx file. Then we manipulate the HRef attribute of the HtmlAnchor control in an event handler (an event handler is a subroutine that executes code for a given event). The Page_Load event is one of many events that ASP.NET understands:
| <script runat="server"> Sub Page_Load link1.HRef="http://www.w3schools.com" End Sub </script> <html> <body> <form runat="server"> <a id="link1" runat="server">Visit W3Schools!</a> </form> </body> </html> |
The executable code itself has been moved outside the HTML.
ASP.NET - Web Server Controls
Web server controls are special ASP.NET tags understood by the server.
Like HTML server controls, Web server controls are also created on the server and they require a runat="server" attribute to work. However, Web server controls do not necessarily map to any existing HTML elements and they may represent more complex elements.
The syntax for creating a Web server control is:
| <asp:control_name id="some_id" runat="server" /> |
In the following example we declare a Button server control in an .aspx file. Then we create an event handler for the Click event which changes the text on the button:
| <script runat="server"> Sub submit(Source As Object, e As EventArgs) button1.Text="You clicked me!" End Sub </script> <html> <body> <form runat="server"> <asp:Button id="button1" Text="Click me!" runat="server" OnClick="submit"/> </form> </body> </html> |
ASP.NET - Validation Server Controls
Validation server controls are used to validate user-input. If the user-input does not pass validation, it will display an error message to the user.
Each validation control performs a specific type of validation (like validating against a specific value or a range of values).
By default, page validation is performed when a Button, ImageButton, or LinkButton control is clicked. You can prevent validation when a button control is clicked by setting the CausesValidation property to false.
The syntax for creating a Validation server control is:
| <asp:control_name id="some_id" runat="server" /> |
In the following example we declare one TextBox control, one Button control, and one RangeValidator control in an .aspx file. If validation fails, the text "The value must be from 1 to 100!" will be displayed in the RangeValidator control:
Example
| <html> <body> <form runat="server"> <p>Enter a number from 1 to 100: <asp:TextBox id="tbox1" runat="server" /> <br /><br /> <asp:Button Text="Submit" runat="server" /> </p> <p> <asp:RangeValidator ControlToValidate="tbox1" MinimumValue="1" MaximumValue="100" Type="Integer" Text="The value must be from 1 to 100!" runat="server" /> </p> </form> </body> </html> |
ASP.NET - Event Handlers
Look at the following code:
| <% lbl1.Text="The date and time is " & now() %> <html> <body> <form runat="server"> <h3><asp:label id="lbl1" runat="server" /></h3> </form> </body> </html> |
When will the code above be executed? The answer is: "You don't know..."
The Page_Load Event
The Page_Load event is one of many events that ASP.NET understands. The Page_Load event is triggered when a page loads, and ASP.NET will automatically call the subroutine Page_Load, and execute the code inside it:
Example
|
Note: The Page_Load event contains no object references or event arguments!
The Page.IsPostBack Property
The Page_Load subroutine runs EVERY time the page is loaded. If you want to execute the code in the Page_Load subroutine only the FIRST time the page is loaded, you can use the Page.IsPostBack property. If the Page.IsPostBack property is false, the page is loaded for the first time, if it is true, the page is posted back to the server (i.e. from a button click on a form):
Example
|
The example above will write the "The date and time is...." message only the first time the page is loaded. When a user clicks on the Submit button, the submit subroutine will write "Hello World!" to the second label, but the date and time in the first label will not change.
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