What are the difference between ASP and ASP.Net?
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Answer Posted / chauhan rakesh botad
Difference between ASP.NET and ASP
Dear friends here is a list of differences of the ASP.NET
technology and the classic ASP technology.Hope it is
informative. Please send your feedback or/and add if you
have additional information.
Introduction
These are the list of differences which I came across while
working on ASPand ASP.NET projects.
Background
I have seen many articles on Internet where in I came across
the differences of ASP.NET and ASP. These articles are
jumbled across the websites. I have compiled all those and
published this article to give better understanding on the
differences of both.
Description
Process Isolation
ASP is run under the inetinfo.exe(IIS) process space and
hence susceptible to application crashes as a result the IIS
needs to be stopped or restarted. ASP is related to the
process isolation setting in IIS.
But, ASP.Net
The ASP.NET worker process is a distinct worker process,
aspnet_wp.exe, separate from inetinfo.exe ( IIS process),
and the process model in ASP.NET is unrelated to process
isolation settings in IIS.
Note :- IIS is still the entry point to a ASP.NET application
Non-MS Platform Support
Classical ASP had no mechanism of running itself on non-
Microsoft technology platforms like the 'The Apache Web Server'
But, ASP.NET
ASP.NET could be run on non-Microsoft Platforms also.
Cassini is a sample Web server produced by Microsoft which,
among other projects, has been used to host ASP.NET with Apache.
Multi Language Support in WebPage
In ASP only two languages were available for scripting
VBScript and Jscript/Javascript.
But in ASP.NET
We are no longer constrained to the two scripting languages
available in traditional ASP: Any fully compliant .NET
language can now be used with ASP.NET, including C# and VB.NET.
Note :- (C# and VB.Net are both server Side languages.)
Interpretation Vs Compilation
In ASP, ASP engine executes server-side code, which is
always through an interpreter (JScript or VBScript). When a
traditional ASP page is requested, the text of that page is
parsed linearly. All content that is not server-side script
is rendered as is back to the response. All server-side
script in the page is first run through the appropriate
interpreter (JScript or VBScript), the output of which is
then rendered back to the response. This architecture
affects the efficiency of page rendering in several ways.
First, interpreting the server-side script on the fly.As a
side effect, one common optimization for ASP applications is to
move a lot of server-side script into precompiled COM
components to improve response times. A second efficiency
concern is that intermingling server-side evaluation blocks
with static HTML is less efficient than evaluating a single
server-side script block, because the interpreter has to be
invoked over and over again. Thus, to improve efficiency of
rendering, many ASP developers resort to large blocks of
server-side script, replacing static HTML elements with
Response.Write() invocations instead. Finally, this ASP
model actually allows different blocks of script within a
page to be written in different script languages. While this
may be appealing in some ways, it also degrades performance
by requiring that a particular page load both scripting
engines to
process a request, which takes more time and memory than
using just one language.
But in ASP.NET,
In contrast, ASP.NET pages are always compiled into .NET
classes housed within assemblies. This class includes all of
the server-side code and the static HTML, so once a page is
accessed for the first time (or any page within a particular
directory is accessed), subsequent rendering of that page is
serviced by executing compiled code. This eliminates all the
inefficiencies of the scripting model of traditional ASP.
There is no longer any performance difference between
compiled components and server-side code embedded within a
page they are now both compiled components. There is also no
performance difference between interspersing server-side
code blocks among static HTML elements, and writing large
blocks of server-side code and using
Response.Write() for static HTML content. Also, because the
.aspx file is parsed into a single code file and compiled,
it is not possible to use multiple server-side languages
within a single .aspx file.
Debugging benefits
In classic ASP it was very difficult for us to debug the
application. ASP developers had time to debug application
due to limited support due to the interpreted model.
But in ASP.NET In addition to improved performance over the
interpreted model, pages that are compiled into classes can
be debugged using the same debugging tools available to
desktop applications or component developers. Errors with
pages are generated as compiler errors, and there is a good
chance that most errors will be found at compilation time
instead of runtime, because VB.NET and C# are both strongly
typed languages. Plus, all the tools available to the .NET
developer are applicable to the .aspx developer.
Server-Side code placement Web Page
class=docText>Especially if you are using ASP pages it is
possible to include executable code outside the scope of a
function within a script block marked as runat=server, and ,
it is possible to define a function within a pair of
server-side script tags.
But in ASP.NET,
In ASP.NET it is no longer possible to include executable
code outside the scope of a function within a script block
marked as runat=server, and conversely, it is no longer
possible to define a function within a pair of server-side
script tags.
Note also that the generated class definition provides
a default constructor for you, and if you try to define your
own default constructor within your page, it will cause a
compiler error. This can be somewhat frustrating if you are
trying to properly initialize elements of your class (such
as filling up our array of values or subscribing to events).
Fortunately, an alternative technique gives you more
complete control over the class definition while separating
the layout from the page logic. This technique is called
code-behind.
Deployment Strategies
In traditional ASP applications, components used by pages
and deployed in this fashion were notoriously difficult to
update or replace. Whenever the application was up and
running, it held a reference to the component file so to
replace that file, you had to shut down IIS (temporarily
taking your Web server offline), replace the file, and
restart IIS.
But in ASP.NET,
The goals of ASP.NET was to eliminate the need to stop the
running Web application whenever components of that
application need to be updated or replaced that is, updating
an application should be as simple as using xcopy to replace
the components on the Web server with the new updated
versions. To achieve this xcopy deployment capability, the
designers of ASP.NET had to ensure two things: first, that
the running application not hold a reference to the
component file and second, that whenever the component file
was replaced with a new version, that new version was picked
up with any subsequent requests made to the application.
Both of these goals are achieved by using the shadow copy
mechanism provided by the Common Language Runtime (CLR).
Shadow copying of assemblies is something you can configure
when you create a new application domain in .NET. The
AppDomainSetup class (used to initialize an AppDomain)
exposes a Boolean property called ShadowCopyFiles and a
string property called CachePath, and the AppDomain class
exposes a method called SetShadowCopyPath() to enable shadow
copying for a particular application domain. The Boolean
property turns the mechanism on for a particular application
domain, the CachePath specifies the base directory where the
shadowed copies should be placed, and the
SetShadowCopyPath() method specifies which directories
should have shadow copying enabled.
ASP.NET creates a distinct application domain for each
application it hosts in its worker process and for each
application domain, it enables shadow copying of all
assemblies referenced in the /bin directory. Instead of
loading assemblies directly from the /bin directory, the
assembly loader physically copies the referenced assembly to
a separate directory (also indicated in the configuration
settings for that application domain) and loads it from
there. This mechanism also keeps track of where the assembly
came from, so if a new version of that assembly is ever
placed in the original /bin directory, it will be recopied
into the Noteshadow" directory and newly referenced from there.
In addition to shadow copying of assemblies, ASP.NET needs
the ability to create and load assemblies on the fly. The
first time an .aspx page is referenced, as we have seen, it
is compiled into an assembly and loaded by ASP.NET. What we
haven't seen is where those assemblies are located once they
are compiled. Application domains also support the concept
of a "dynamic directory" specified through the DynamicBase
property of the AppDomainSetup class, which is a directory
designed for dynamically generated assemblies that can then
be referenced by the assembly loader. ASP.NET sets the
dynamic directory of each application it houses to a
subdirectory under the system Temporary ASP.NET Files
directory with the name of the virtual directory of that
application.
One consequence of both dynamic assembly generation and
shadow copying is that many assemblies are copied during the
lifetime of an ASP.NET application. The assemblies that are
no longer being referenced should be cleaned up so that disk
space usage doesn't become a limiting factor in application
growth. In ASP.NET shadow copied assemblies are removed as
soon as possible after a new version of that assembly is
copied, and dynamically generated assemblies that are no
longer used are cleaned up the next time the ASP.NET worker
process is bounced and the particular application associated
with the dynamic assemblies is run again. In general, this
means that you shouldn't have to worry about unused
assemblies generated by ASP.NET wasting space on your
machine for very long.
New Page Directives
In ASP you must place all directives on the first line of a
page within the same delimiting block. For example:
<%LANGUAGE="VBSCRIPT" CODEPAGE="932"%>
But in ASP.NET, you are now required to place the Language
directive with a Page directive, as follows:
<%@Page Language="VB" CodePage="932"%> <%@QutputCache
Duration="60" VaryByParam="none" %>
You can have as many lines of directives as you need.
Directives may be located anywhere in your .apsx file but
standard practice is to place them at the beginning of the
file. Several new directives have been added in ASP.NET. I
encourage you to look these up in the ASP.NET documentation
to see how they may benefit your application.
Threading Issues
The threading model of COM object created using VB within a
web-based application is STA. ASP worker thread resides in
its own STA and hence the compatability is fine in this case
with a little performance hit.
But in ASP.NET,
The ASP.NET threading model is the Multiple Threaded
Apartment (MTA). What this means is that components that you
are using that were created for the Single Threaded
Apartment (STA) will no longer perform or function reliably
without taking some extra precautions in ASP.NET. This
includes, but is not limited to, all COM components that
have been created using Visual Basic 6.0 and earlier
versions. You will be glad to hear that you can still use
these STA components without having to change any code. What
you need to do is include the compatibility attribute
aspcompat=true in a <%@Page> tag on the ASP.NET page. For
example, <%@Page aspcompat=true Language=VB%>. Using this
attribute will force your page to execute in STA mode, thus
ensuring your component will continue to function correctly.
If you attempt to use an STA component without specifying
this tag, the run time will throw an exception. Setting this
attribute to true will also allow your page to call COM+ 1.0
components that require access to the unmanaged ASP built-in
objects. These are accessible via the ObjectContext object.
If you set this tag to true, your performance will degrade
slightly. I suggest doing this only if you absolutely need to.
Validation & Browser scripting capabilities
* ASP has no inbuilt facility for Validation of
controls.i.e, checking whether a textbox is left blank or
not or a combo is selected or not or if a phone number does
not fit a particular pattern for a area and many such examples.
* The user had to write the client side Javascript code
for all these kind of validations.
* Client and server side validation both were the
headache of the of the developer.
* Javascript code to fit a particular Browser was also
the developer's burden. He had to write specific code so
that it could fit a set of browsers. It took lot of the
developers time.
But in ASP.NET,
In built validation controls are provided which are as easy
to implement and the developer has to worry the least.
The features provided by ASP.NET validation controls is :-
* Browser Independent coding :- Developer does not have
to worry about the browser how the controls would render to.
* Client-Side or Server-Side :- The Validation Controls
manage the code checking if the client side code is disabled
the validation is done on the server side.
Rich Validation set :- There are 6 types of validation which
cater to the needs of the validation requirements:
* RequiredFieldValidation Control - Requires that the
control not be left blank.
* CompareValidator Control - Used to compare Data in Two
Controls
* RangeValidator Control - Used to check for Range
validation.(also supports various data Type - Date , string
etc..)
* RegularExpressionValidator Control - Used to check the
complicated patterns in the user input.
* CustomValidator Control- The final control we have
included in ASP.NET is one that adds great flexibility to
our validation abilities. We have a custom validator where
we get to write out own functions and pass the control value
to this function.
This control also provides Client side and server side
validation of which the Server side validation could be a
different function altogether.
* Validation Summary - The validation summary control
will collect all the error messages of all the non-valid
controls and put them in a tidy list. The list can be either
shown on the web page (as shown in the example above) or
with a popup box
Conclusion
This article targets to the developers who have directly
started working on ASP.Net and also for the web developers
who have migrated from ASP to ASP.Net. This article is at
the draft level and might need additions which I intend to
do.I welcome suggestion or criticism!! I would request to
add as much feedback to this article post as possible. I
would keep this post updated.
References
* A very indepth look at the differences. - Excellent.
* (W3Schools - Good article)
* A Comprehensive Description of the Difference- Worth
Reading
* A brief difference - Very Good
License
This article has no explicit license attached to it but may
contain usage terms in the article text or the download
files themselves. If in doubt please contact the author via
the discussion board below.
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