Introduction to ASP.NET
• Some references:
–
–
–
–
Beginning ASP.NET using VB.NET; Wrox; 2002 chpt 2.
Kalata, K, Introduction to ASP.NET – 2002, chpt 1.
Esposito, D. Programming Microsoft ASP.NET, chpt 1.
Morrison, M. and Morrison, J. Database driven web sites
(2nd edn). Chpt 6.
– VS.NET on line documentation + Quickstart tutorials
Introduction to ASP.NET
• What is ASP.NET and how is different
from ASP
– ASP: server side technology for creating dynamic
web pages using scripting languages eg vb script.
– ASP.NET: server side technology for creating
dynamic web pages using Fully Fledged
programming languages supported by .NET
– VB.NET: our chosen language for writing
ASP.NET pages
What is .NET?
•
•
A Microsoft strategy and new technology for delivering software
services to the desktop and to the web
Components include:
– MS Intermediate Language; all code is complied into a more abstract,
–
–
–
–
•
•
•
trimmed version before execution. All .NET languages are compiled to
MSIL – the common language of .NET
The CLR- common language runtime; responsible for executing MSIL
code; interfaces to Windows and IIS
A rich set of libraries (Framework Class Libraries) available to all .NET
languages
The .NET languages such as C#, VB.NET etc that conform to CLR
ASP.NET is how the Framework is exposed to the web, using IIS to
manage simple pages of code so that they can be complied into full .NET
programs. These generate HTML for the browser.
Built on open protocols (XML, SOAP)
Future for development of MS & non-MS based systems.
Also heading towards the “Internet Operating System”
Common Language
Runtime Type System
Compilers use the runtime type system to produce type
compatible components
Components
C#
VB
C++
Common Type System
Compilers
Runtime Environment
Robust And Secure
•
Native code compilation



•
Code correctness and type-safety


•
MSIL
No interpreter
Install-time or run-time IL to native compilation
IL can be verified to guarantee type-safety
No unsafe casts, no uninitialized variables, no out-of-bounds array
indexing
Evidence-based security

Policy grants permissions based on evidence (signatures, origin)
.NET Execution Model
VB
Native
Code
VC
...
Script
IL
Common Language Runtime
Standard JIT
Compiler
Native
Code
Common Language Runtime
• Lightweight Just-in-time compiler:
– MSIL to Native machine language; Can be ported to numerous
platforms
• 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
Framework Overview
VB
C++
C#
JScript
…
Common Language Specification
Win Forms
Data and XML
Base Class Library
Common Language Runtime
Visual Studio.NET
Web Forms
(ASP.NET)
.NET Framework Architecture
System.WinForms
System.Web
Web Services
Web Forms
ASP.NET Application Services
Controls
Drawing
Windows Application Services
System Base Framework
ADO.NET
XML
SQL
Threading
IO
Net
Security
ServiceProcess
Common Language Runtime
Type System
Metadata
Execution
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
Importing Namespaces
• Visual Studio .NET adds references to your projects’
commonly used namespaces by default
• You can import the namespaces into your page using
the @Import 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 %>
Some ASP.NET namespaces
System
Defines fundamental data types eg
system.string
System.Collections
Definitions and classes for creating
various collections
System.IO
File reading & writing operations
System.Web
Support browser/server communication
System.Web.UI
Creates the Page object whenever an
.aspx page is requested
System.Web.UI.webcon Classes and definitions to create server
trols
controls
ASP.NET – class browser
• ASP.NET provides a means of exposing the .NET
Framework and its functionality to the WWW
• Contains a number of pre-built types that take
input from .NET types and represents them in a
form for the web (such as HTML)
• Class browser (over 9000 classes; lists the
namespaces):
http://interdev.csse.monash.edu.au/quickstart/aspp
lus/samples/classbrowser/vb/classbrowser.aspx
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
WebForms
• The ASP.NET WebForm is separated into two
logical areas:
– The HTML template
– A collection of code behind the WebForm
• The HTML template
–
–
–
–
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
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
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." />
HTML Server Vs
ASP.NET Server, Controls
• ASP.NET form controls can interact with clientside 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"
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 a navigation bar
• 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
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
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
Server controls with Visual Studio.NET
The Code Behind
• 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)
Code Behind file
• The location of the code behind the page is determined via a
property that is set on the first line in the page using the @Page
directive
<%@ Page Language="vb" Codebehind="WebForm1.vb"
Inherits=“MyFirstApp.WebForm1"%>
• The @Page 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 file
• The Inherits property indicates that the code behind the page
inherits the page class
• This page class contains the compiled code for this page
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
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
Page class events
• Page_init
• Page_load
•
Server_Controls
•
Page_prerender
•
Page_Unload
Web Services
• Web Services also provide a means to
expose .NET functionality on the web but
Web Services expose functionality via
XML and SOAP (cf: function calls over the
web)
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
http://www.xmethods.com
How ASP.NET works
• When .NET is installed, IIS is configured to look
for files with the .aspx extension and to use the
ASP.NET module (aspnet_isapi.dll) to handle
them.
• ASP.NET parses the .aspx file and arranges it in a
predefined class definition and generates an
asp.net page object.
• The page object generates html that is sent back to
IIS and then the browser.
• NOTE: only .aspx files are parsed (if it is pure
html don’t save it as an aspx file as it will slow
down the server.
ASP.NET samples
• Page directives: <%@ page language = “VB” debug="true"
trace="true“ %>
• <script language = “VB” runat=“server”> VB.NET code
declarations ……….. </script>
• Message.aspx
<html>
<head> <title>Inserting ASP.NET code Example</title> </head>
<body>
Line1: First HTML Line<br />
Line2: Second HTML Line<br />
Line3: Third HTML Line<br />
</body>
</html>
• Note this has no asp code so better to use .html extension
• Message2.aspx
<script language="VB" runat="server">
Sub Page_Load()
Response.Write ("First ASP.NET Line<br />")
Response.Write ("Second ASP.NET Line<br />")
Response.Write ("Third ASP.NET Line<br />")
End Sub
</script>
<html> <head> <title>Inserting ASP.NET code Example</TITLE> </head>
<body>
Line1: First HTML Line<br />
Line2: Second HTML Line<br />
Line3: Third HTML Line<br />
</body>
</html>
• Message3.aspx
html>
<head><title>Inserting ASP.NET code Example</title></head>
<body>
Line1: First HTML Line<br />
Line2: Second HTML Line<br />
Line3: Third HTML Line<br />
<script language="VB" runat="server">
Sub Page_Load()
Response.Write ("First ASP.NET Line<br />")
Response.Write ("Second ASP.NET Line<br />")
Response.Write ("Third ASP.NET Line<br />")
End Sub
</script>
</body>
</html>
Render or inline code block –
interweave1.aspx
<html>
<head>
<title>Interweaving ASP.NET code and HTML Example</title>
</head>
<body>
Line1: First HTML Line<br />
<% Response.Write ("First ASP.NET Line<br />") %>
Line2: Second HTML Line<br />
<% Response.Write ("Second ASP.NET Line<br />") %>
Line3: Third HTML Line<br />
<% Response.Write ("Third ASP.NET Line<br />") %>
</body>
</html>
NOT RECOMMENDED.
Interweave2.aspx A Server control
<script language="VB" runat="server">
Sub Page_Load()
Message.Text="The ASP.NET line"
End Sub
</script>
<html>
<head> <title>Inserting ASP.NET code Example</TITLE> </head>
<body>
First HTML Line<br/>
<asp:label id=Message runat="server"/> <br />
Second HTML Line<br/>
</body>
</html>
Web application project files
AssemblyInfo.vb
Info about the compiled project file stored in
/bin and named project.dll
Global.asax
Event handler commands visible to all web
forms in a project
Global.asax.resx
Define application resources such as text
strings, images. Can change without
recompiling project.
Global.asax.vb
Asp.net code for application events eg
session.start
Project.sln
Stores links to all project files
Project.suo
VS.NET IDE configuration info for the proj.
Project.vbproj
Configuration and build settings for project
files.
Web application project files cont.
Project.vbproj.webinfo
URL to project web server
Project.vsdisco
Enables search for web services
Styles.css
Project style sheet
Web.config
Project and folder configuration information
Webform.aspx
Web form .aspx file;Html
Webform.aspx.resx
Resources in corresponding web form
Webform.aspx.vb
Code written for the form (code behind)
Bin\project.dll
Compiled project output file (assembly)
Bin\project.pdb
Debugging information used by developer
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
Using the ILDASM to
View the Assembly and Classes
Using the ILDASM to view the assembly and classes
Examples
• quickstart – webforms
–
–
–
–
–
–
–
Intro4 shows VIEWSTATE
Intro6 shows a click event
Intro7 shows a usercontrol with a calander
Intro8 shows a db connection
Intro9 & 10 show asp.net templates
Intro11shows validation controls
Intro13 shows code behind pages
• Server directives eg trace and debug
– trace
The lab environment.
• Each machine is set up to be an IIS server –
http://localhost:1900/…..
• You create your web projects with Visual Studio.Net.
VS.NET will create a subdirectory in c:/inetpub/wwwroot
for your project. You must copy this subdirectory when
moving to another machine or home.
• URL
– http://localhost:1900/MyfirstApp/homepage.aspx
• Alternative to VS.Net is webmatrix
• Some samples on another machine
– http://interdev.csse.monash.edu.au/cse2030/ Interdev is not
accessible outside the Monash network.
ASP.NET Vs PHP
Feature
PHP
ASP.NET
HTML
Yes
Yes
CSS
Yes
Yes
‘php Templates’
Yes
UserControls
ServerControls
(buttons,grids etc)
No
Yes
Javascript
Yes
Yes + Validation controls
Database Conn
Yes
Yes
Cookies & Sessions
Yes
Yes
VIEWSTATE
No
Yes
POSTBACK
No
Yes