ASP.Net

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ASP.Net
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ASP and .Net

• .Net is a collection of libraries, templates and
  services designed to make programming
  applications of all kinds, easier, more flexible
  (multi platform), and more scalable
• ASP.Net is a subset of .Net that contains tools
  for developing web based applications

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Client/Server Overview

• A server is a program that makes services
  available to another program (a client)
• For instance, A web server such as IIS (Internet
  Information Server) or Apache makes web pages
  available to a client application such as a
  browser
• A database server makes data available to client
  that makes a valid request

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Client/Server Overview Cont.

• ASP.Net pages are served from IIS when a browser
  requests an .apsx page.
• IIS passes the request to .Net which processes
  the C or VB code and ASP controls, makes any
  database requests and renders them into xhtml
• IIS then sends the rendered page to the browser
  that made the request

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ASP.Net Server/Client
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elements of an ASP Page

• The Page
• Web Form
• Html and ASP.Net Controls
• Code behind
• CSS

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The Page

• The page is the container for everything else
• An ASP application can contain several pages
• Usually the starting page is called
  Default.aspx
• Every page begins with a directive
• lt_at_ Page Language"C" AutoEventWireup"true"
  CodeFile"Default.aspx.cs" Inherits"_Default" gt
• This directive tells IIS that the page is an
  ASP.Net application

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The web form

• An ASP. Page can have only 1 form.
• A key attribute of the form is runatserver
  which tells IIS to send it to .Net for compiling
  and rendering. (Plain html elements are just
  passed through to the client without any .net
  processing)
• All asp controls must be contained within the form

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HTML and ASP Controls

• An ASP.Net page can use
• plain xhtml
• Xhtml controls (xhtml with the runatserver
  attribute added)
• ASP.Net controls, controls provided by .Net
  Library
• Client side JavaScript

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Design and Source views

• ASP.net pages have two views Design and Source
• Design view shows controls approximately as they
  will appear on the rendered page (some info shown
  here wont be displayed)
• Source view shows the html and the asp.net
  controls.
• ASP controls are represented as XML fragments
• Controls can be added in Design or source views

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XML Fragment of an ASP Control

• ltaspLabel ID"Label1" runat"server" Text"Enter
  the Miles"gtlt/aspLabelgt

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Code Behind

• ASP.Net allows you to write the code in a
  separate file.
• This makes code easier to read and maintain
• The page directive tells .Net where to find the
  code page.
• Code can still be placed directly in the web page
  if you wish either between ltscriptgt tags or
  between lt gt brackets

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CSS

• ASP.Net supports CSS and has a good CSS editor
• CSS classes and styles can be added to a ASP
  control by using the CssClass attribute
• ltaspTextBox ID"txtMiles" runat"server"
  CssClass"entry"gtlt/aspTextBoxgt

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ASP Pages and State

• ASP.Net, like all web pages are stateless.
• Every time you click and button or use control
  that causes postback the page is re-rendered from
  the server
• Information is not retained between postbacks
  without some additional programming. (Windows
  forms have state. They keep their variable values
  and contents in RAM)
• This has several implications for web application
  development that we will have to examine later