Ch 04 asp.net application

ASP.NET Application

Anatomy of ASP.NET
application
 global.asax Application file
 ASP.NET Configuration
 .NET Components,
Extending the HTTP Pipeline

In traditional desktop programming,
an application is an executable file
with related support files. (EXE & DLL
Files) and other resources such as
databases and configuration files.

ASP.NET application is a combination
of files, pages, handlers, modules, and
executable code that can be invoked
from a virtual directory.

Anatomy of an ASP.NET
Application
 Unlike a Windows application, the end user
never runs an ASP.NET application directly.

 The web server has no concept of separate
applications - it simply passes the request to the
ASP.NET worker process.

 Web pages that are hosted in the same virtual
directory (or one of its subdirectories) execute in
the same application domain.

 A virtual directory is simply a directory that’s
exposed through a web server.

The Application Domain
 An application domain is a boundary enforced by the CLR
that ensures that one application can’t influence (or see the
in-memory data) of another.

 The following characteristics are a direct result of the
application domain mode.

 All the web pages in a single web application share the
same in-memory resources, such as global application
data, per-user session data, and cached data.

 All the web pages in a single web application share the
same core configuration settings.

 All web applications raise global application events at
various stages.

The Application Domain cont..
 ASP.NET applications can include all of the following
ingredients.

 Web pages (.aspx files)

 Web services (.asmx files)

 Code-behind files

 A configuration file (web.config)

 global.asax

 Other components (components developed or
third-party components with useful functionality)

Application Lifetime
 ASP.NET uses a lazy initialization technique
for creating application domains.
 Means that the application domain for a web
application is created the first time a request is
received for a page in that application.
 An application domain can shut down for a
variety of reasons, including if the web server
itself shuts down.
 ASP.NET automatically recycles application
domains when you change the application.

Application Lifetime cont..
ASP.NET application may be periodically
recycled when certain thresholds are
reached.

 This model is designed to keep an
application healthy

 And to detect characteristics that could
indicate a problem has developed or
performance of the application has
degraded.

Application Updates
 Can update your web application without needing
to restart the web server and without worrying
about harming existing clients.
 Transits to a new application domain when
web.config configuration file is modified.
 ASP.NET doesn’t actually use the ASP.NET files in
the virtual directory.
 Instead, it uses another technique, called
shadow copy, (uses files in
c:WindowsMicrosoft.NETv2.0.50727Temporar
y ASP.NET Files)
 ASP.NET’s ability to detect when you change the
original files (relies Windows operating system)

Application Directory Structure

Every web application should have a
well-planned directory structure.
 Independently from the directory
structure designed, ASP.NET defines a
few directories with special meanings.

Application Directory Structure
cont..

The global.asax Application File
 The global.asax file allows you to write event handlers
that react to global events.
 Users cann’t request the global.asax file directly.
 Instead, the global.asax file executes its code
automatically in response to certain application events.
 global.asax doesn’t contain any HTML or ASP.NET tags.
 It contains methods with specific, predefined names.
 Every global.asax file defines the methods for a single
class—the application class (class derives from
HttpApplication)
 The global.asax file is optional, but a web application can
have only one global.asax file.

The global.asax Application File
cont..
 global.asax must reside in the root directory of
the application, not in a subdirectory.

 An application event handler is just to use the
recognized method name (as opposed to web
controls events).

 ASP.NET automatically calls methods in
global.asax when the application event occurs.

 ASP.NET creates a pool of application objects
when your application domain is first loaded
and uses one to serve each request.

Application Events
 Developer can handle two types of
events in the global.asax file:
 Events that always occur for every
request. These include request-related
and response related events.
 Events that occur only under certain
conditions.

Application Events cont..
 Avoid use of use the Application_Error()
method to control the appearance of a web
page. (without coding painstaking conditional
logic)

 Instead, you would probably configure
custom error pages using the web.config file.

 Application_Error() might be extremely
useful for logging an error for future
reference or even send an e-mail about error
to a system administrator

ASP.NET Configuration
 Configuration in ASP.NETis managed with
XML configuration files.

 The ASP.NET configuration files have several
advantages over traditional ASP configuration
 They are never locked.

 They are easily accessed and replicated.

 They are easy to edit and understand

 No need of configuration tool

The machine.config File
 machine.config that resides in the directory
c:Windows
Microsoft.NETFrameworkv2.0.50727Config.
 defines supported configuration file sections,
configures the ASP.NET worker process, and registers
providers that can be used for advanced features such as
profiles, membership, and role-based security
 <processModel>
 This section allows you to configure how the
ASP.NET worker process recycles application domains,
 <machineKey>
 This section allows you to set the server-specific key
used for encrypting data and creating digital signatures.

The web.config File
 Every web application inherits the settings
from the machine.config file and the root
web.config file

 For example, you might want to set a specific
method for authentication, a type of
debugging, a default language, or custom
error pages.

 web.config file in a web application can’t
override all the settings in the machine.config
file

The web.config File cont..
 Basic skeletal structure of the web.config file
<?xml version="1.0"?>
<configuration>
<appSettings />
<connectionStrings />
<system.web>

</system.web>
</configuration>

Configuration Inheritance
 The default machine.config settings are applied first.
 The web.config settings from the computer root are
applied next. This web.config file is in
 the same Config directory as the machine.config file.
 If there is a web.config file in the application root A,
these settings are applied next.
 If there is a web.config file in the subdirectory B, these
settings are applied next.
 If there is a web.config file in the subdirectory C, these
settings are applied last.

Configuration Inheritance cont..

The web.config file cont..
 <customErrors>
allows you to configure the behavior of
your application in response to various
HTTP
errors.

For Example
<customErrors
defaultRedirect="standarderror.aspx"
mode="RemoteOnly">
<error statusCode="404"
redirect="filenotfound.htm"/>
</customErrors>

The web.config file cont..
 The following is a list of the modes
supported for the mode attribute:
 On: Indicates that custom errors are
enabled. If no defaultRedirect attribute is
supplied, users will see a generic error.
 Off: Custom errors are disabled. This
allows full error details to be displayed.
 RemoteOnly: Custom errors are shown
only to remote clients while full detailed
errors are displayed to local clients.

The web.config file
(<system.web> Settings)

The web.config file
(<system.web> Settings)
 <configuration>
 <connectionStrings>
 <add name="NorthwindConnection”
connectionString=
 "Data Source=localhost;Integrated
Security=SSPI;Initial
Catalog=Northwind;"
 providerName="System.Data.SqlClient
" />
 </connectionStrings>
 <system.web>...</system.web>
 </configuration>

Reading and Writing Configuration Sections Programmatically

 ASP.NET provides the
WebConfigurationManager class in the
System.Web.Configuration namespace,
which allows you to extract information
from a configuration file at runtime.

Reading and Writing Configuration Sections Programmatically

 Forexample, if you’re retrieving information from the
<authentication> section, you’ll receive an
AuthenticationSection object, as shown here:

// Get the configuration for the current web application.

Configuration config =
WebConfigurationManager.OpenWebConfiguration("/");

// Search for the <authentication> element inside the
<system.web> element.

AuthenticationSection authSection =
(AuthenticationSection)config.GetSection(@"system.web/
authentication");

The Website
Administration Tool (WAT)
 Letsyou configure various parts of the
web.config file using a web-page
interface.
 To run the WAT to configure the current
web application in Visual Studio, select
Website ➤ ASP.NET Configuration (or
Project ➤ ASP.NET Configuration if
you’re using projectbased development).
 Can use the WAT to automate the
web.config changes

Extending the HTTP
Pipeline
 The pipeline of application events isn’t
limited to requests for .aspx web forms.
 One example is if you want to create a
web resource that dynamically renders a
custom graphic.
 In this situation, you simply need to
receive a request, check the URL
parameters, and then return raw image
data as a JPEG or GIF file.

Ch 04 asp.net application

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