Chapter 1: An Introduction To ASP.NET Web Programming Liu, Jie Professor Department of Computer Science Western Oregon University Liuj@wou.edu

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 Port Domain name 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 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 users over Internet Any Browser Remote Systems Over Internet Any Hardware/OS Local users Traditional Window application This picture is to show the architecture of the technology at a conceptual level. Some language compilers are included in the .Net framework. Others such as Cobol would have to be purchased. Java and or J## (Microsoft’s Java Language) would have to be installed separately. .Net Framework ASP.NET Application Services Windows Forms Controls Windows Application Services Web Forms Web 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 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