Review Materi ASP.NET

3SC – Q6 Dudy Fathan Ali S.Kom
Review Materi ASP.NET
3SC – Q6
Dudy Fathan Ali, S.Kom (DFA)
2014
CEP - CCIT
Fakultas Teknik Universitas Indonesia

Consuming Web Services in a Web Application
Web services are the application components that
can be used by other Web applications.
You can create a Web service and publish it on a Web
server, thereby, making it available for other Web
applications to use.

Invoking Web Services
A Web service:
Is a self-describing Web component that exposes its functionality to
the consumers through open standards such as XML and Simple
Object Access Protocol (SOAP).
Is a widely used method for implementing Service-Oriented
Architecture (SOA).
Allows integration of applications developed in different languages
and running on different platforms.
Communicates by using a standard protocol called SOAP. SOAP defines
a standard way of passing the XML-encoded data.
Developing ASP.NET Web services starts by creating an .asmx
file and hosting it on a Web server, such as IIS.
A Web service once hosted or published on the server can be
consumed by any client.

Invoking Web Services
The client locates the service by adding a Web reference.
This adds a proxy class on the client side, which exposes the
methods, parameters, and return types of the methods
contained in the Web service.
After adding the proxy class, the client application creates an
instance of the proxy class and accesses the methods provided
by the Web service through the instance.
The client requests are then handled by the proxy class.
After processing the request, the response is also sent as a
SOAP message to the proxy.
The proxy then converts this SOAP message into method return
value, which is returned to the client.

Invoking Windows Communication Foundation Services
In distributed computing, Web services along with various other
technologies, such as COM+, .NET Remoting, Message Queues,
and Web Service Enhancement (WSE) were used to provide a
wide range of functionality.
WCF:
Unifies features of such discreet technologies under one single
framework.
Provides a unified programming model used to build a secure, reliable,
and robust Web service.
Aims at providing encoding, hosting, messaging patterns, networking,
security, and interoperability in a single infrastructure.

The following figure shows the WCF architecture.

The following set of APIs is unified in the WCF architecture:
ASP.NET Web Services (ASMX)
WSE
System.Messaging
Enterprise Services
Remoting
The design goals for building WCF services are:
Unification
Interoperability
Service orientation

Creating Rich Internet Applications Using AJAX
AJAX is a technology, which when implemented in
Web applications makes the interaction between the
client and the server asynchronous.
AJAX implementation:
Allows users to interact with the Web application while
waiting for a response from the server.
Enables partial updates in Web applications.
Explaining the AJAX Framework

AJAX is a Web development technique that:
Is used for creating dynamically interactive applications.
Enables Web applications to retrieve data from the server,
asynchronously in the background, without interfering with
the display and behavior of the existing page.
To understand the concept of AJAX, you need to
understand the relevance of the following terms:
Asynchronous communication
JavaScript
XML
Understanding AJAX

AJAX-enabled Web applications offer:
Quick response to a user’s request
Asynchronous communication that allows a user to
interact with the rest of the Web page while the
application is processing the changed or updated parts of
the Web page
Auto-generated proxy classes that are used to call Web
service methods from client script such as JavaScript
Support for the widely used Web browsers such as
Microsoft Internet Explorer, Mozilla Firefox, and Apple
Safari
Advantages of AJAX-Enabled Web Applications

Some of the limitations of AJAX-enabled Web
applications are:
Browser Integration
Dependency on JavaScript
Limitations of AJAX-Enabled Web Applications

The ASP.NET AJAX Web applications consist of client-side and
server-side scripts.
The following figure displays the ASP.NET AJAX architecture.
Architecture of ASP.NET AJAX

The preceding figure shows that the ASP.NET AJAX
architecture consists of the following components:
Client-based Microsoft AJAX library
Server-based AJAX features for ASP.NET

Client-based Microsoft AJAX library:
The ASP.NET AJAX client architecture provides features that
enable you to create rich, intuitive, responsive, and
interactive Web applications. This architecture includes the
ASP.NET AJAX library that includes:
Components
Browser compatibility
Networking
Core services

Server-based AJAX features for ASP.NET:
The ASP.NET AJAX server architecture provides the
functionalities for the following server-based AJAX
features:
Script support
Web services
Application services
Server controls

Implementing Internationalization and Accessibility
Implementing Internationalization
To make an international application customizable, you need to
understand the following phases that are involved in developing an
internationalized application:
• Globalization: Globalization is the process of designing and
developing a Web application in such a way that it is culture-neutral
and language-neutral.
• Localizability: Localizability is an intermediate process that ensures
that a globalized Web application is ready for implementing
localization.
• Localization: Localization is the process of customizing the
globalized Web application to a specific locale and culture. In this
phase, various resources, such as images and text, for the
designated locale are created.

Factors Related to Creating International Applications
Application developers need to attend to locale considerations
when they develop international applications because negligence
of these considerations can lead to issues. The factors that need
to be considered while designing an internationalized application
are:
• Language issues
• Formatting issues
• String-related issues
• User-interface issues

Language issues
Languages around the world differ in display, alphabets,
grammar, and syntactical rules. For example, some languages
such as Arabic are written from right-to-left, whereas other
languages are written from left-to-right. Some languages include
uppercase and lowercase characters, whereas others do not even
have the concept of uppercase and lowercase. Languages differ in
the number of characters, storage requirements, keyboard
layouts, and code representations. This diversity makes it difficult
to share data between cultures. It is even more difficult to create
a multilingual user interface.

Formatting issues
Formatting is the main source of differences in applications
designed for multiple languages or cultures. Formatting
differences may arise in the addresses, currency, dates,
numerals, telephone numbers, time, and units of measure of
various languages.

String-related issues
When developing international applications, programmers must
consider issues related to strings. When strings are translated
from one language to another, the translated strings may be
longer than the original strings. In strings, the order of alphabets
varies in different languages. This causes major problems in
sorting and comparison of strings. Issues also arise when strings
are concatenated because these strings may convey different
meanings in different languages.

User-interface issues
Various user interfaces are associated with the design of an
international application. The size of user interface elements
should be larger than that required for accommodating
English strings. This is because strings in other languages are
usually longer than strings in the English language. When
messages grow in size as a result of translation to another
language, they should be allowed to wrap to subsequent lines.
You should also ensure that all the access-key and shortcut-key
combinations are available on international keyboards. This is
because every language has a different keyboard layout, and
some characters do not exist on all keyboards.

Implementing Accessibility
Accessibility:
Refers to the degree of ease with which an application can be used by a
variety of people.
Helps people having disabilities to work with the application easily.
Enables users to interact with the application more efficiently.
ASP.NET provides some guidelines that you should consider
while designing your Web application to achieve high
accessibility.

Fundamentals of Designing an Accessible Application
The features of a Web application that are used frequently
should have a high degree of accessibility.
Therefore, a developer should strictly follow the accessibility
guidelines while designing this feature.
The principles that should be followed while implementing
accessibility support in an application are:
Flexible user interface
Flexible input and output features
Simple and Intuitive

Accessibility Design Guidelines for the Web
Some guidelines for implementing accessibility in an
application are:
Standardize font styles
Support keyboard navigation
Standardize the use of images
Standardize the use of tables
Minimize the use of style sheets
Use controls properly

Assistive Technologies Used for Accessibility of the Web
People with disabilities use various assistive technologies for
accessing a Web application.
Some assistive technologies used by the people with
disabilities are:
Braille and refreshable Braille
Scanning software
Screen magnifiers
Screen readers
Visual notifier

Securing Web Applications
Introducing the ASP.NET Security Model
The ASP.NET security model:
Allows you to implement security in your Web
applications.
Provides restricted levels of access to secure website
information from unauthorized access.
Helps in maintaining data integrity and confidentiality.

The following figure displays the architecture of the ASP.NET
security model.
Web Clients
ASP.NET Applications
.NET Framework
Windows Operating System
IIS

The working of the ASP.NET security model is described in the
following steps:
1. Internet Information Services (IIS) receives a request from a Web
client.
2. IIS attempts to authenticate the user.
3. If ASP.NET authenticates the user, it allows requests to the specified
Web page.
4. When the ASP.NET code requests resources, the operating system
performs its own security checks to verify that the authenticated user
is allowed access to the specified file and directory.
5. If access is granted, the requested resource is returned through IIS.

Configuring IIS for Implementing Security
IIS authenticates the user who has requested for the application by using
a specific type of authentication.
The type of authentication depends on how the security for Web
applications is configured on IIS.
You need to configure security on IIS to authenticate users before they
are permitted access to a Web application.
IIS provides the following types of authentication to control access to
your Web application:
Anonymous
Basic
Digest
Integrated Windows

Configuring an ASP.NET Application for Security
ASP.NET uses its own security mechanism to authenticate
users.
To be able to use ASP.NET security mechanism, you need to
configure the security settings in the web.config file of the
Web application.
These security settings include configuring authentication,
authorization, and impersonation for accessing resources in
your application.

Configuring Authentication
Authentication is the process of validating the identity of a
user before granting access to a restricted resource.
Authentication in a Web application can be configured by
using the <authentication> element in the web.config
file.
The <authentication> element specifies the
authentication type that is used by an application to
authenticate the user.
The authentication type can be specified by using the mode
attribute of the <authentication> element.

Configuring Authentication
The mode attribute can have the following values:
Windows: This mode specifies that the authentication is performed
by IIS by using basic, digest, or Integrated Windows authentication.
Forms: This mode specifies that the user will be authenticated by
using form-based authentication method.
Passport: This mode specifies that the user will be authenticated by
using Microsoft Passport authentication method.
None: This mode specifies that no authentication mechanism is set
and that any anonymous user can access the Web application.

Configuring Impersonation
When a user requests an ASP.NET application, the request goes
to IIS.
IIS authenticates the user and forwards the request to ASP.NET.
If ASP.NET impersonation is disabled, irrespective of the user
who has logged on, the ASP.NET application will be executed by
using a fixed machine-specific account.
In Windows XP, this account is automatically created by
ASP.NET and is named as ASPNET.

Configuring Impersonation
Impersonation is the process of executing code under the
authenticated user identity and not under the ASPNET
account.
Impersonation involves the following steps:
1. When a request from a remote client is received, IIS carries out
authentication. If the client is authenticated, it passes the request to
the ASP.NET application.
2. The application impersonates the client and uses the authentication
given by IIS to access the restricted resources.
3. If authorized to access resources, the ASP.NET application returns the
requested resources to the client through IIS.

Tracing and Monitoring Web Applications
Implementing Tracing in Web Applications
To ensure that the application is working properly and is not
giving unexpected results, you need to keep track of the
execution of your Web application.
ASP.NET provides you with the tracing feature that enables
you to track the program execution, thereby ensuring that
your Web application runs properly.
You can use tracing feature to:
View diagnostic information about a particular Web page.
Display custom tracing information about the execution of an
application.

Tracing can be implemented at any of the following
levels:
Page level
Application level

Page-level tracing:
Page-level tracing is used to generate diagnostic
information at the end of page rendering.
The diagnostic information includes all the information
about the requests made to the page and their responses.
To enable page-level tracing, you need to perform the
following steps:
1. Include the following directive at the top of the page:
<%@ Page Trace="True" %>
2. Include the TraceMode attribute in the @ Page directive to
specify the sort order for your trace messages.

The following information is displayed when page-level tracing is
enabled:
Request details
Trace information
Control tree
Session state
Application state
Request Cookies Collection
Response Cookies Collection
Headers Collection
Response Headers Collection
Form Collection
Querystring Collection
Server Variables

Application-level tracing:
Application-level tracing is used to trace information for every Web page in a
Web application.
A special page named trace.axd is used to view this trace information.
To use the trace.axd page, you have to first enable
application-level tracing within the Web.config file for your application.
You can use the following attributes of the <trace> element to change the
tracing settings of your website:
enabled
requestLimit
pageOutput
traceMode
localOnly
mostRecent

Writing Trace Information
When a Web application is in the development stage, you
often use several Response.Write statements in the
program code to display debugging information, which is used
to troubleshoot the application.
The messages displayed using Response.Write
statements are required for debugging and should not be
displayed to an end user.
The process of tracing enables you to insert debugging code
within an application such that the debugging code does not
need to be removed at the time of deployment.
The Trace property of the Page class returns a Trace
object, which can be used to write custom trace statements.

Writing Trace Information
The Trace object:
Is an instance of the TraceContext class.
Provides a set of methods and properties that help you to trace the
execution of your application.
The properties of the Trace object are:
IsEnabled: Denotes whether tracing is enabled for the current
request.
TraceMode: Sets the trace modes such as sortByCategory or
sortByTime.
Some of the methods of the Trace object are:
Warn: Displays the trace information in red color.
Write: Displays the trace information in black color.

Using Trace Listeners
Trace listeners are used to:
Collect, store, and route tracing messages.
Redirect the tracing information to logs, windows, or text files.
ASP.NET provides three types of predefined trace listeners:
TextWriterTraceListener
EventLogTraceListener
DefaultTraceListener

Adding a trace listener:
To add a trace listener in the web.config file, you need to include the
following markup in the web.config file:
<configuration>
<system.diagnostics>
<trace>
<listeners>
<add name="MyListener"
type="System.Diagnostics.
TextWriterTraceListener"
initializeData="D:myListener.txt" />
</listeners>
</trace>
</system.diagnostics>
</configuration>

To enable ASP.NET to route tracing information to a
System.Diagnostics listener, you need to include the
following entry in the web.config file:
<system.web>
<trace writeToDiagnosticsTrace = “true” />
<customErrors mode=”off” />
</system.web>

Removing a trace listener:
To remove a trace listener from the listeners collection, you need to
include the following markup in the web.config file:
<configuration>
<system.diagnostics>
<trace>
<listeners>
<remove name="MyListener"/>
</listeners>
</trace>
</system.diagnostics>
</configuration>

You can control the tracing output by using trace switches.
Trace switches can be configured to provide filtered tracing output.
You can also enable and disable certain tracing output using trace switches.
The two types of trace switches are:
BooleanSwitch
TraceSwitch
To initialize a TraceSwitch, you need to first create its object.
The following code snippet shows how you can create and initialize a
TraceSwitch:
System.Diagnostics.TraceSwitch MyTraceSwitch = new
System.Diagnostics.TraceSwitch("MySwitch", "Entire
application");

Monitoring Web Applications
After deploying a Web application, a System Administrator
needs to constantly monitor the application for its proper
functioning.
By monitoring a Web application, you can detect the problems
occurring in the application and troubleshoot them.
Monitoring and troubleshooting are required to improve the
performance of a Web application.
To help you track monitor a Web application, ASP.NET provides
you with the following two features:
Health monitoring
Performance monitoring

Health Monitoring
ASP.NET health monitoring system:
Enables you to monitor the status of the deployed Web
applications.
Is used to track system events and errors, which can hamper
the performance of a Web application.
Enables you to get the detailed run-time information about
ASP.NET resources used by a Web application.
Is implemented by using the System.Web.Management
namespace.

Health Monitoring
You can configure applications to use built-in or
customized monitoring providers.
To use the health monitoring system you need to:
Configure and enable Web events to monitor.
Configure and enable event providers that listen for and
process various Web events.
Web events contain information about the health of a
Web application.

Health Monitoring
There are several events that you can trap to monitor the
health of a Web application. Some of the important events
are:
WebBaseEvent
WebBaseErrorEvent
WebHeartbeatEvent
WebRequestEvent
WebErrorEvent
WebApplicationLifetimeEvent
WebRequestErrorEvent
WebAuditEvent
WebFailureAuditEvent

Health Monitoring
The event providers are used to listen for Web events that are
raised by a Web application. Some of the built-in providers are:
EventLogWebEventProvider
SqlWebEventProvider
SimpleMailWebEventProvider and TemplatedMailWebEventProvider
TraceWebEventProvider
WmiWebEventProvider

Performance Monitoring
Performance is an important factor in making a Web
application or project successful.
You need to monitor a Web application to troubleshoot any
performance-related issues.
You need to keep a track of such errors to improve the
performance of your Web application.
ASP.NET provides you with several performance counters,
such as Application Restarts, Requests Queued, and Errors
Total to help you keep track of the execution of your Web
application.

ASP.NET supports the following two groups of performance
counters:
System performance counters
Application performance counters

The following table lists some of the system performance
counters.
System Performance Counter Description
Application Running Represents the number of applications running
simultaneously on a Web server.
Requests Disconnected Represents the number of requests that have been
disconnected due to a communication failure.
Request Wait Time Represents the number of milliseconds that the most
recent request waited in the queue for being processed by
the server.
State Server Sessions Active Represents the number of user sessions that have become
inactive because of some user action. This counter is
available only on the computer where the state server
service, aspnet_state is running.
Worker Process Running Represents the number of worker processes running on a
Web server.

The following table lists some of the application performance
counters.
Application Performance Counter Description
Anonymous Requests Represents the number of requests that are using
anonymous authentication.
Anonymous Requests/Sec Represents the number of requests per second that
are using anonymous authentication.
Cache Total Entries Represents the total number of entries in the
cache.
Cache Total Hits Represents the total number of hits from the cache.
Debugging Requests Represents the number of requests that occur while
debugging is enabled.

Thank You!
Dudy Fathan Ali S.Kom
dudy.fathan@eng.ui.ac.id
Source : NIIT Courseware Q6M2

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