ASP .NET BASICS

Lesson Objectives : 
Introduces more 
advanced ASP.Net topics
such as:
           # ASP.Net Page Structure
# ASP.Net Server Controls
# Directives
# View State
# Name spaces
# ASP.Net Page Structure 
An ASP.Net page consists of the following elements:
# Directives
# Code declaration blocks
# Code render blocks
# ASP.Net server controls
# Server-side comments
# Server-side include directives
# Literal text and HTML tags
# Not every element always appears on a given page, we will learn when to use them
# Directives :
# Control how the page is compiled
# Specify settings when transferring between pages
# Aid in debugging
# Allow importing of classes
# Start with the <@ sequence and end with a %> sequence
# ASP.Net directives can appear anywhere on the page, but are usually placed as the first lines in the file
Three Common Directives :
# The Page directive defines page-specific attributes like the language to be used as in:
# <%@ Page Language=“C#” %>
# The Import directive makes functionality defined elsewhere through the use of namespaces as in:
# <%@ Import Namespace=“System.Web.Mail” %>
# The Register directive links a user control to the ASP.Net page as in:
# <%@ Register TagPrefix=“ux” TagName=“footer” Src=“footer.ascx” %>
#  Code Declaration Blocks :
# When you add programming logic to your .aspx page, it resides inside a
  <script runat=“server”> tag
# Code declaration tags usually are placed in the <head> of your ASP.Net page
# If you don’t specify the language of the code, it will default to the language in the Page directive
 # <script runat=“server” language=“C#”>
# Code Render Blocks :
# Used to define inline code or inline expressions
# <% String Title = “Harry Potter”; %>
# <% Title %>
# The first line contains a complete line of C# code, the declaration and assignment of a String variable
# The second line writes out the Title variable onto the page

# ASP.Net Server Controls :
# Server Controls represent the dynamic elements users interact with.
# There are four types of server controls:
# HTML Controls
# ASP.Net Controls
# Validation Controls
# User Controls
# Most server controls must reside within a
  <form runat=“server> tag


# Advantages of Server Controls :

# HTML elements can be accessed from within code to change their 
        characteristics, check their values, or dynamically update them

# ASP.Net controls retain their properties even after the page was processed.  This process is called the View State

# With ASP.Net controls, developers can separate the presentational elements and the application logic so they can be considered separately

# What is the View State??? :

# The persistence of data after it is sent to the server for processing is possible because of the View State

# If you have created forms using HTML controls, you have experienced the loss of data after form submission

# The data is maintained in the view state by encrypting it within a hidden form field

# looking at the view state :

# Look at the source code of the file after the page has been submitted to see code similar to this…

# i.e.  <input type= hidden” name=“VIEWSTATE” value=“dWtMTcy0TAy0DawNzt)PDtsPGk6Mj47PjtsPHQ802w8aTWzPj+02wPGw5uAXJdGFaGaxk6t4=“ />

# The View State is enabled for every page by default

# If you don’t intend to use the View State, set the EnableViewState property of the Page directive to be false

# <%@ Page EnableViewState=“False” %>

Server-Side Comments :

# Server-side comments will not be processed by ASP.Net

It used the <%-- beginning sequence and the --%> ending sequence

<% --  This is a server-side comment --%>

#The difference between HTML comments and ASP.Net comments is that ASP.Net comments are processed by the browser or the ASP.Net runtime

#Don’t use HTML comments to comment out ASP.Net code

#HTML comments only hide things from the browser

Server-Side Include Directives :

#These includes help developers insert segments of code into a page from an external file

#There are two techniques for doing this:

#Using the file attribute, we give the physical path to the file on the server either as an absolute path starting from the drive letter or a relative path to the current file

#<! -- include file=“myinclude.aspx”  -->  (relative path)

#Using the virtual attribute, you can specify the file’s location from the absolute root of the site, or from a relative path to the current page.

#<! -- include virtual=“/directory1/myinclude.aspx” --> 

(absolute path

Literal Text and HTML Tag :

#One cannot do without text and HTML elements to display information from your ASP.Net controls and programming code

#Without these there would be no format to the page

#The surrounding <html>, <head>, and <body> tags make it possible for a browser to understand our page

ASP.NET LANGUAGES :

# .Net supports many different languages

#Programmers used to VBScript or JavaScript to do their programming will have more robust, strongly-typed, and feature-rich choices in VB.Net and C#.Net

#VB.Net builds on the RAD that became popular in the 90’s.  VB.Net is easy to read, use and maintain.

# C#.Net was developed to keep the simplicity of VB and the power and flexibility of C++ (some say to replace Java).  C# does away with confusing C++ syntax.

Summary :

# On an ASP.Net page,
you will probably use: directives, code declaration blocks, code render blocks, includes, comments, and controls.
# Two languages supported by ASP.Net are VB.Net and C#.Net.  We will focus on C#.Net syntax for this course.
# In the next chapter we will cover some C# programming basics.






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