Chapter 1 An Introduction To ASP NET Web

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 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 • • • 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#" Auto. Event. Wireup="true" Code. File="Default. aspx. cs" Inherits="_Default" %> Auto. Event. Wireup allows Page_Load linked with page load event and called when the page is loaded § The. ASPX. CS page using System. Web. UI. Html. Controls; public partial class _Default : System. Web. UI. Page { protected void Page_Load(object sender, Event. Args e) { … … if (Is. Post. Back) … …

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 n. Temp 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. 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 str. Fruit = "oranges, apples, peaches, kumquats, nectarines, mangos"; // Declare an array. string[] arr. Fruit; // Place each word in an array element. arr. Fruit = str. Fruit. Split(new Char [] {', ', ': '}); // Sort the array. System. Array. Sort(arr. Fruit); // Put the sorted array back in the string. str. Fruit = System. String. Join(" ", arr. Fruit);

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