Migration from ASP to ASP.NET can drastically improve the performance of your applications.
A software created using ASP.NET is more robust, scalable, reliable, and secure as compared
to the software created using ASP. ASP.NET, which is a new version of ASP, removes all the
shortcomings of ASP. For example, it removes tier confusion from the code (by providing an easy
way to separate presentation layer, business logic layer, and database layer), it allows code
compilation instead of code interpretation, and provides CLR (Common Language Runtime) for
built in garbage collection to avoid memory leaks.
ASP.NET, which uses .NET Framework, enables you to build globally distributed applications with
Internet functionality and interoperability built into them. ASP.NET enables you to build
platform independent software that can be easily integrated with any application developed on
any platform and language that supports CLR. The .NET platforms now support approximately
25 .NET compatible languages as compared to ASP, which can support only two scripting
languages -- VBScript and JavaScript.
ASP to ASP.NET migration can open a whole new world of possibilities for your web-based
applications. For example, you can make use of already existing XML web services in your code
to add a new feature or functionality to your code. XML Web services can be utility programs
created by any developer and can be made available through Internet world wide without
worrying about the operating system and programming language used to create them. Consider a
situation where you want to validate the credit card number of your online customers on your
website. Instead of writing the code to validate the credit card numbers of the customers
yourself, you can simply plug in the already available Web service providing credit card
validation in your code.
In addition, the ASP.NET migration can make the code of your application considerably small,
easily manageable, and easily deployable. This white paper discusses the benefits that you may
get, after the migration of your application from ASP to ASP.NET.
It provides all the valuable information in understanding the important aspects of migration from
ASP to ASP.NET and provides a clear insight into the benefits of proposed migration. This paper
will help you understand the complexities of a migration and explain how to enable a
smooth .NET migration of your ASP code.
Furthermore this paper discusses the issues that you must consider before considering a migration
and the various migration strategies available.
Benefits of ASP to ASP.NET Migration
Microsoft's .NET Framework is rapidly gaining momentum as a standard for business systems,
both within an organization and for the external clients of an organization. The advantages of
migration of your existing applications to ASP.NET are enormous and disadvantages are none.
This is because all the features of asp are available in ASP.NET. Installing ASP.NET does not break
your existing ASP applications. ASP.NET uses a separate file name extension (.aspx instead of
.asp), separate configuration settings, and an entirely separate runtime technology. With an ASP
application entire web server may go down if one application crashes but ASP.NET processes run
in a different server space and in separate application domain. This saves entire web server to
crash just because of one application. If ASP and ASP.NET are installed on the same computer,
ASP pages and applications can continue to use the existing ASP engine, with no interference
from ASP.NET.
Some other benefits of ASP to ASP.NET Migration are:
Better Language Support: ASP.NET is platform independent technology and supports 25 .NET
languages such as C#, VB.NET, and JavaScript. .NET Developers can visually create Web pages
with the use of VB style drag drop feature in Visual Studio.NET IDE. They can use built in
debugging, testing and deployment features of .NET platform for easy manageability of code. In
addition developers can use over 4500 .NET framework classes that provides a number of
controls for performance monitoring, logging, file upload, image generation, XML processing,
data access, transactions, regular expressions, message queuing, SMTP mail and much more.
Event-Driven Programming: ASP.NET is an object oriented technology that supports event
driven programming unlike ASP. Objects on a Web page can expose events that can be processed
by ASP.NET code. Load, Click and Change events handled by code makes coding much simpler
and better organized.
Improved Scalability: ASP.NET has removed the bottlenecks created by ASP sessions, which
used to work well only on the server where they were created. They used to store the session
data "in-process" on the web server, which was a cause of scalability bottlenecks on high-volume
sites. ASP.NET stores session's data on a dedicated state server that can be easily shared by
multiple web servers and on an SQL Server database too, providing a better scalability and
availability of sessions. This has improved the server to server communication, making it possible
to scale an application over several servers. One example of this is the ability to run XML
parsers, XSL transformations and even resource hungry session objects on other servers.
Improved Performance: ASP.NET highly improves the performance of your code because it
uses caching in code with automatic content expiration. This feature automatically expires and
refreshes data from the cache. This automatically solves the problems of memory leaks from
your application and improves the performance of your application. ASP.NET performs dynamic
compiled execution of code, which allows fast retrieval of pages as compared to ASP, which
requires each page to be interpreted when it is requested by the client. The dynamic
compilation automatically detects changes in the code and stores the compiled code in memory
to serve the future requests by the web server.
Easier Configuration and Deployment: ASP.NET use XML (extensible markup language) file
within the application to store application configurations. The configuration files used by
ASP.NET applications can be changed and uploaded while the application is running without
restarting the server. The web applications are simply copied to the server without the need to
run regsvr32 to register any application components and configuration settings.
Easier Code Maintenance: ASP.NET enables easy code maintenance because it separates
presentation layer from business logic layer. Developers with relevant expertise in front end and
back end programming can easily maintain code as compared to ASP, where a single file is used
to write HTML, VB script, Java script, and ASP code.
Fundamental Changes in Code
Both ASP and ASP.NET can coexist with each other. ASP and ASP.NET applications can run side by
side on a server without having adverse affect on each other. Both applications use separate file
extensions, configuration models, and processing engines. For example an ASP application uses
.asp extension and a .NET application uses .aspx extension. The configuration in ASP is done
using registry but ASP.NET uses XML-based configuration files. You can have one part of
an application running ASP and another part of the same application running ASP.NET. All these
features are very beneficial if you need to move a large, rapidly changing site to ASP.NET one
piece at a time.
The fundamental changes that may occur in the code after migration can be categorized into
following categories:
Core API Changes: These changes refer to the changes made to the API method calls while
migration. For example the changes that would occur when you make the calls related to
Request, Response, and Server objects. Usually the method of making calls is same but if there
are multiple values for a given key for collection objects different method to return the
collection of values is used.
Structural Changes: These changes refer to the changes that affect the layout and coding style
of an application. For example ASP.NET pages only support one language on a single page where
as ASP allowed multiple languages to be used on a single page. ASP.NET page functions must be
declared in <script runat=server> blocks where as in ASP, page functions are declared within <%
%> blocks. In ASP.NET, page functions must be declared in <script runat=server> blocks whereas
ASP.NET does not support page-render functions.
Visual Basic Language Changes: VB.NET is a complete programming language as compared to
VB Script that was used in ASP. Some of the changes include the removed use of VARIANT data
type and Option Explicit. The variable declared with VARIANT data type needs to be transformed
to some basic data types. The Option Explicit is made a default feature. Some other keywords
such as LET and SET are not supported and Integer values are now 32 bits and Long types have
become 64 bits.
COM-Related Changes: VB.NET code migration does not force you to incorporate any
COM-related changes in your code. Most of these changes are back stage changes and are done
automatically. Some changes include the change in threading model, early binding and late
binding changes, and changes in OnStartPage and OnEndPage methods in the code.
Application Configuration Changes: ASP.NET requires you to store all your configuration
settings in Web.config file, which is available in the main application directory.
State Management Issues: ASP.NET does not require you to change your Session or Application
objects. On the other hand it provides State Management Options for Inproc, StateServer,
SqlServer for improved control on your applications. If your application is partially migrated to
.NET platform then you cannot share state variables stored in the intrinsic Session or Application
objects in your application with .NET pages. You need to duplicate this information in both
systems, till the complete migration takes place.
Security-Related Changes: ASP.NET supports Windows, Passport, and Forms-based
authentication, including cookie management and automatic redirecting of unauthorized logins.
All these authentication methods were also available in ASP but Passport based authentication in
a new feature added to ASP.NET. Unlike ASP, ASP.NET does not do per-request impersonation. It
does not allow your code to run on behalf of authenticated user. You can still use your old
authentication methods and perform custom user and login checking using other authentication
methods.
Data Access: ASP.NET uses ADO .NET, which offers an enormous range of features as compared
to ADO to improve your data access methods. It offers powerful new features to get you data
from database. Though you need not make any code changes for migration but you can make use
of all ADO.NET features in your code.
Migrating Existing Applications to ASP.NET
Although migration of your existing applications to ASP.Net can be very beneficial, sometimes
people are reluctant to make this transition. This may be due to many reasons. One of ASP's
great assets is that it allows you to use a very simple scripting language, which is not the case
with .NET platform. .NET uses modern, full-featured programming languages. ASP.NET therefore
places much greater demands on web developers, compared to those placed on conventional
software developers.
In ASP, executing the principles of good design is extremely difficult. ASP applications are
complex and difficult to maintain, with very low code re-use. On the other hand with .NET there
is an opportunity to produce better-designed applications, with resulting benefits in sustaining
the quality.
However these design skills are new demands on ASP programmers, and have a long and steep
learning curve. While it is very much possible to write ASP.NET applications in the ASP style, this
will reverse many of the advantages of .NET technology.
Developers who have not come from a traditional software development background may require
more extensive training to adapt to the new concepts. Even experienced software developers
may not have fully used object orientated features previously. There could be performance
scaling down and productivity decline while developers get accustomed to .NET.
Facts to Consider Before Migration
Before you go for a migration you must determine the benefits that you expect from the
migration and the time that you can afford to spare for the migration process. You must also
understand the complexity of migration in your application. If you have a big application with
number of modules, the quality of the code, the use of COM components, and the distribution of
data access functions in the code are few important factors that must be considered before you
go for migration.
The greatest difficulty in all programming is good design. If your code has a good design and the
multi-tiered separation exists in your application code then the migration process can be smooth
else the migration process will be complex and would require a huge amount of effort. A good
code design implies that the presentation layer is separated from the business components
layers and data access functions reside centrally in data tier.
Changing an ASP page's file extension from .asp to .aspx and correcting for some syntactical
changes is usually enough to get an ASP page working as an ASP.NET page. Such an approach,
although it can be completed quickly, does not take advantage of many of the new features of
.NET, including ASP.NET Web controls, Microsoft ADO.NET, the Microsoft .NET Framework classes.
It is better to follow a complete lifecycle of migration and evaluate the complexity of
your code to provide the best ASP.NET migration solution for your ASP code.
Although the complete migration of a site in one go is possible, it is often better to use a
modular approach. The decision to go for a modular migration or full fledged migration is based
on the size and complexity of the application. The simple and small web sites can be migrated to
.NET platform in one go but big, complex, and mission critical business applications should be
migrated using a modular approach.
Migration Strategies
If a company is going to put forth the effort to move their software to ASP.NET
platform then this migration may be a long-term investment for the company.
This can be an opportunity to make as many architectural and design improvements as possible in
the existing code. In such a scenario, a phased approach for migration is must,
where both ASP and ASP.NET modules coexist, till complete migration takes place.
If a company is looking for long-term benefits from the migration then the
company can follow the approaches given below:
Co-Existence
In this approach, you can have the ASP and ASP.NET modules existing together.
You can perform migration for a specific functionality of an application and ensure that the
migrated module would still interoperate with the existing application. At Hanu, we follow the
following co-existence strategies:
Migrating Shared Pages: In this approach we select only those pages first that share their code
with other pages. These pages are common pages having intensive code processing and the
potential for caching. This enables the important and complete sections of the applications to be
migrated first. After this migration both ASP and ASP.NET would be running simultaneously and
ASP pages will be using ASP.NET code.
Migrating New Pages: In this approach we select only those pages, which need to be added to
the application for additional functionality. These pages can be entirely new pages or existing
pages that require major code changes. This is the most comfortable approach without affecting
the existing functionality. This also restricts new bugs to the new pages only.
Migrating Entire Tier or Entire Module: In this approach, we either select an entire module for
migration or migrate the application tier by tier. This can be done using Horizontal and Vertical
migration strategies. Both these migration strategies will be discussed in the next section of this
paper.
Build the Roadmap
In this approach, to get long term benefits of migration, you decide to
invest in re-architecting a system so that you can make the best use of .NET framework. The
primary objective of this approach is to provide a comprehensive and detailed design for future
project developments.
Full Fledged
In this approach you may want a full fledged migration of your system with the
plans for change in application design, development, and deployment. This may be due to some
strategic business needs.
There are basically two co-existence migration strategies: Vertical and Horizontal Migration.
Both of these strategies offer a modular approach for migration.
Vertical Migration
Vertical migration refers to migrating an application one tier at a time, as shown in the Figure
given below. For example, consider you have a three tier HR application, which consist of three
modules, Recruitment, Leaves Management, and Salary Management. The three tiers used by the
application include the user interface, business components, and database.
Vertical migration approach would proceed through all the pages of the user interface tier for
each module, followed by the business component and data interface tiers, as shown in the
figure given below:
The vertical migration is most appropriate when the application's modules are tightly coupled
and minimal changes are required to the interfaces between application tiers. The initial
architectural review in this case could yield opportunities for shared code across all three tiers
rather than result in separating the modules into distinct applications.
Horizontal Migration
Horizontal migration refers to migration of an application module by module, completing the
migration for all three tiers of one module before moving on to the next. As shown in the Figure
given below. For example Horizontal migration would proceed through entire Recruitment
Module first with all the three tiers (user interface, business components, and database)
migrating together for that module. After the recruitment module is completely migrated the
other two modules Leaves Management, and Salary Management will be migrated.
A horizontal migration is most appropriate when application modules are loosely coupled and
when interfacing between different application tiers is a tedious task. An architectural review all
of the application's modules should be conducted before any module migration begins. This
review should uncover opportunities for creating reusable code, and may lead to separating the
modules into independent applications.
Migration Life Cycle
We believe that no tool currently available is capable of providing a smooth and complte
migration process. Tools can be used for basic migration but advanced migration
requirements of the code can only be fulfilled using manual intervention in code.
The complete migration lifecycle consists of four main stages.
Analysis: At this stage, you analyze the existing code, and create a migration strategy.
You should consider the scope of migration, the processes required for migration such
as code modification and testing plans. At this stage you should also identify the
.NET specific functionality that can be added to the application or can be replaced with ASP.NET functionality.
Conversion: At this stage, you perform the actual code conversion. Start developing and
modifying modules for migration. You should also perform unit testing and peer reviews for the
converted code.
Re-factoring: At this stage, you perform code optimization and design improvement. This stage
can actually enable you to get long terms gains from the migration and can be helpful in
drastically improving the performance of the application.
Testing: At this stage you should conduct functional and non-functional testing for the modules that
have been successfully migrated.
The complete life cycle of the migration process ensures a smooth migration of your system from
ASP to ASP.NET
About the Authors
The following Hanu Software Employees contributed to the development of this white paper
Manoj Srivastava - Practice Manager, having a tenacious IT experience, helps clients to
develop business application to leverage .NET platform.
Amit Kataria - Consultant, Focuses on .NET development projects, Management Scholar from
renowned Indian College.
About Hanu Software:
Hanu Software is a global IT consulting and services provider, with corporate business offices
located in Princeton, New Jersey and engineering campuses located in Gurgaon, India. Founded
in 2002, our firm is dedicated to developing effective outsourcing partnerships with clients in order
to reduce their IT costs, improve process management and reduce time-to-market for new
product ideas. We provide end-to-end software solutions in a variety of industry verticals,
including publishing, finance, real estate, insurance, retail and others.
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