Asp .net web form fundamentals

ASP .NET
Web Form Fundamentals

For Beginners
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ASP.NET Application
An ASP.NET application is a combination of files,
pages, handlers, modules, and executable
code that can be invoked from a virtual
directory (and, optionally, its subdirectories)
on a web server. In other words, the virtual
directory is the basic grouping structure that
delimits an application.


ASP.NET File Types


ASP.NET Application Directories


Server Controls
• Server controls are created and configured as
objects. They run on the web server and they
automatically provide their own HTML output.
• Server controls behave like their Windows
counterparts by maintaining state and raising
events that you can react to in code.
• ASP.NET actually provides two sets of server-
side controls that you can incorporate into
your web forms.


HTML server controls & Web controls
• HTML server controls: These are server-based equivalents
for standard HTML elements.
– These controls are ideal if you’re a seasoned web programmer
who prefers to work with familiar HTML tags (at least at first).
– They are also useful when migrating ordinary HTML pages or
ASP pages to ASP.NET, because they require the fewest changes.
• Web controls: These are similar to the HTML server
controls, but they provide a richer object model with a
variety of properties for style and formatting details.
– They also provide more events and more closely resemble the
controls used for Windows development.
– Web controls also feature some user interface elements that
have no direct HTML equivalent, such as the GridView, Calendar,
and validation controls.


HTML Server Controls
• HTML server controls provide an object interface for standard HTML elements.
They provide three key features:
• They generate their own interface: You set properties in code, and the underlying
HTML tag is created automatically when the page is rendered and sent to the
client.
• They retain their state: Because the Web is stateless, ordinary web pages need to
do a lot of work to store information between requests.
– HTML server controls handle this task automatically. For example, if the user selects an item in
a list box, that item remains selected the next time the page is generated.
– Or, if your code changes the text in a button, the new text sticks the next time the page is
posted back to the web server.
• They fire server-side events: For example, buttons fire an event when clicked, text
boxes fire an event when the text they contain is modified, and so on.
– Your code can respond to these events, just like ordinary controls in a Windows application. In
ASP code, everything is grouped into one block that executes from start to finish.
– With event-based programming, you can easily respond to individual user actions and create
more structured code.
– If a given event doesn’t occur, the event-handler code won’t be executed.


The HTML Control Classes


Important HTML Control Properties


How ASP .NET Application Works
• First, the request for the page is sent to the web server. If you’re running a
live site, the web server is almost certainly IIS. If you’re running the page
in Visual Studio, the request is sent to the built-in test server.
• The web server determines that the .aspx file extension is registered with
ASP.NET and passes it to the ASP.NET worker process. If the file extension
belonged to another service (as it would for .asp or .html files), ASP.NET
would never get involved.
• If this is the first time a page in this application has been requested,
ASP.NET automatically creates the application domain. It also compiles all
the web page code for optimum performance, and caches the compiled
files in the directory c:Windows
Microsoft.NETFrameworkv2.0.50727Temporary ASP.NET Files. If this ask
has already been performed, ASP.NET will reuse the compiled version of
the page.
• The compiled aspx page acts like a miniature program. It starts firing
events (most notably, the Page.Load event). However, you haven’t created
an event handler for that event, so no code runs. At this stage, everything
is working together as a set of in-memory .NET objects.
• When the code is finished, ASP.NET asks every control in the web page to
render itself into the corresponding HTML markup.
• The final page is sent to the user, and the application ends.

The HtmlControl Base Class
• Every HTML control inherits from the base
class HtmlControl. This relationship means
that every HTML control will support a basic
set of properties and features.


The HtmlContainerControl Class
• Any HTML control that requires a closing tag inherits from the HtmlContainer class
(which in turn inherits from the more basic HtmlControl class). For example,
elements such as <a>, <form>, and <div> always use a closing tag, because they
can contain other HTML elements.

• On the other hand, elements such as <img> and <input> are used only as stand-
alone tags. Thus, the HtmlAnchor, HtmlForm, and HtmlGenericControl classes
inherit from

• HtmlContainerControl, while HtmlInputImage and HtmlInputButton do not. The
HtmlContainer control adds two properties to those defined in HtmlControl.


The HtmlInputControl Class
• This control defines some properties that are used for the <input>
element. As you’ve already learned, the <input> element can represent
different controls, depending on the type attribute. The <input
type="text"> element is a text box and <input type="submit"> is a button.


The Page Class
• Every web page is a custom class that inherits
from System.Web.UI.Page.
• By inheriting from this class, your web page
class acquires a number of properties and
methods that your code can use.
• These include properties for enabling caching,
validation, and tracing


Sending the User to a New Page
• Click <a href="newpage.aspx">here</a> to go to
newpage.aspx.
• HttpResponse.Redirect()
– you can get access to the current HttpResponse object
through the Page.Response property.
– Response.Redirect("newpage.aspx");
– Response.Redirect("http://www.prosetech.com");
• HttpServerUtility.Transfer()
– An HttpServerUtility object is provided through the
Page.Server property
– Server.Transfer("newpage.aspx");


HTML Encoding


Application Events


The Global.asax File
• To add a Global.asax file to an application in
Visual Studio, choose Website –> Add New
Item, and select the Global Application Class file
type. Then, click OK.


ASP.NET Configuration
• Every web application includes a web.config file that configures
fundamental settings everything from the way error messages are
shown to the security settings that lock out unwanted visitors.
• The ASP.NET configuration files have several key advantages:
– They are never locked: You can update web.config settings at any
point, even while your application is running. If there are any requests
currently under way, they’ll continue to use the old settings, while
new requests will get the changed settings right away.
– They are easily accessed and replicated: Provided you have the
appropriate network rights, you can change a web.config file from a
remote computer. You can also copy the web.config file and use it to
apply identical settings to another application or another web server
that runs the same application in a web farm scenario.
– The settings are easy to edit and understand: The settings in the
web.config file are humanreadable, which means they can be edited
and understood without needing a special configuration tool.


The web.config File
• The web.config file uses a predefined XML format. The entire
content of the file is nested in a root <configuration> element.
Inside this element are several more subsections, some of which
you’ll never change, and others which are more important.


Nested Configuration
• ASP.NET uses a multilayered configuration system that allows you to
set settings at different levels.
– Every web server starts with some basic settings that are defined in
two configuration files in the
c:WindowsMicrosoft.NETFrameworkv2.0.50727Config directory.

– These two files are machine.config and web.config. Generally, you
won’t edit either of these files manually, because they affect the
entire computer. Instead, you’ll configure the web.config file in your
web application folder. Using that file, you can set additional settings
or override the defaults that are configured in the two system files.

– More interestingly, you can use different settings for different parts of
your application. To use this technique, you need to create additional
subdirectories inside your virtual directory. These subdirectories can
contain their own web.config files with additional settings.


Storing Custom Settings in the
web.config File
• ASP.NET also allows you to store your own settings in the web.config file,
in an element called <appSettings>. Note that the <appSettings> element
is nested in the root <configuration> element.


The custom settings that you add are written as simple string
variables. You might want to use a special web.config
setting for several reasons:
– To centralize an important setting that needs to be used in
many different pages: For example, you could create a variable
that stores a database query. Any page that needs to use this
query can then retrieve this value and use it.
– To make it easy to quickly switch between different modes of
operation: For example, you might create a special debugging
variable. Your web pages could check for this variable and, if it’s
set to a specified value, output additional information to help
you test the application.
– To set some initial values: Depending on the operation, the user
might be able to modify these values, but the web.config file
could supply the defaults.

• You can enter custom settings using an <add> element that
identifies a unique variable name (key) and the variable
contents (value). http://www.rajpatsystems.com

Asp .net web form fundamentals

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