Transcript Chapter 1: An Introduction To ASP.NET Web Programming

Chapter 1: An Introduction To
ASP.NET Web Programming
Liu, Jie
Professor
Department of Computer Science
Western Oregon University
[email protected]
Web Applications
 The Client/Server model -- a computation model for PCs to connect to
other computers, like the monitor and mainframe architecture model.
• Client –sends a request
 Thin client
 Thick client
• Server – answers the requests
 For Web based applications
• Communication are through HTTP (hypertext Transfer Protocol)
 What is a protocol
• Client is a browser such as IE (Internet Explorer)
• A browser displays pages defined using HTML tags (Hypertext, Markup
Language)
 Static pages – not going to change
 Dynamic pages – formed dynamically according to the requests
• The application itself is defined on a web server such as IIS (Internet
Information Services), with in turn may interact with other server such as a
Database Management System (DBMS) that is hosted on a database
server
Web Applications
http://sundown.wou.edu:81/en/mail.html?lang=en&laurel=on&cal=1
Domain name Port
Page/file Parameter #1
Protocol
Path
Start of parameters Parameter #2
Dynamic Pages
 A dynamic page is generated each time it is called
 The same page may be posted back to the server for
processing.
 Nevertheless, the page itself is stateless, i.e., it will not
maintain the value of a variable between each loading of
the page
More About State
 “State” refers to the values of a variable or object
 Variables in a web page is stateless meaning that
they do not “remember” their previous values
 Methods used to maintain a variable’s state
include
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Use view state
Use session or application state object
Using static variable (C# feature)
Use cookie
Use database
(show Website 3 example and Visual Studio)
A Closer Look at the example
 The .ASPX page
• Page directives
<%@ Page Language="C#" AutoEventWireup="true"
CodeFile="Default.aspx.cs" Inherits="_Default" %>
AutoEventWireup allows Page_Load linked with page load event and
called when the page is loaded
 The .ASPX.CS page
using System.Web.UI.HtmlControls;
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
……
if (IsPostBack)
……
A Closer Look at the example
 More about the Visual Studio in coming chapters
 A page and a page behind it (separation of
presentation and business logic)
 Controls, properties, and events
 If I change nTemp to be a static variable, what will
happen?
 Different between design view and source view
The .Net Framework Structure
Remote Systems
Over Internet
Any Hardware/OS
Remote users
over Internet
Any Browser
Local users
Traditional Window
application
.Net Framework
ASP.NET
Web Forms
Web Services
Windows Forms
Controls Windows Application Services
Application Services
.Net Compliant Programming Languages **
VB.NET, C++, C#, J++, etc
.Net Framework Class Library
Common Language Runtime
Operating System
Windows 2000/2003/NT/98/ME/XP and may be other OSs
VB, C#, and J++
// Declare and initialize a string.string
strFruit = "oranges,apples,peaches,kumquats,nectarines,mangos";
// Declare an array.
string[] arrFruit;
// Place each word in an array element.
arrFruit = strFruit.Split(new Char [] {',', '.', ':'});
// Sort the array.
System.Array.Sort(arrFruit);
// Put the sorted array back in the string.
strFruit = System.String.Join(" ", arrFruit);
Summary
 Have general understanding about the following
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Web applications
Web page
Stateless
ASP.NET components (IIS, frame work, CLR, etc)
Client/Server
Dynamic pages
URL
 Helpful web sites
• www.msdn.microsoft.com
• www.Asp.net