Migration from ASP to ASP.NET

Migration from ASP to ASP.NET Anand M. Hegde Developer Support Engineer Microsoft Developer Support Microsoft Corporation

Overview
Why should you migrate?
Introduction to Microsoft® ASP.NET
Key changes from ASP to ASP.NET
Migrating from ASP to ASP.NET
Migrating applications that use COM components
Migrating applications that use databases
Migration best practices
ASP to ASP.NET compatibility FAQ
Resources for ASP.NET and migration

Why Should You Migrate?
Increased scalability and reliability
Minimum 2X to 3X performance gain
Built-in cross-browser compatibility
Rich server-side controls, Microsoft Visual Studio® .NET designer support, and configuration options
X-copy deployment of pages and components
Better debugger; tracing options
Content-code separation
Take advantage of new caching features
Enhanced state-management features
ASP and ASP.NET can run side-by-side if required
Many new features

Before You Migrate
Get a good understanding of ASP.NET
Know the changes from ASP to ASP.NET
Understand that migration requires code changes
Although ASP.NET has excellent backward compatibility, migration may not be as easy as it seems in many cases

Introduction to ASP.NET
ASP.NET is:
A new programming framework for Web applications
An overhaul of ASP
A part of Microsoft .NET
Compiled and event driven programming model
It permits you to:
Rapidly develop powerful Web applications and services
Easily build, deploy, and run Web applications that can target any browser or device
It requires:
Microsoft Windows® 2000 or later for hosting and development

ASP.NET Architecture

ASP.NET Request Flow ASPX engine Gen’d page class file Page class ASPX file Request Parse Generate Instantiate, process, and render Response Request Code behind class file Response Instantiate

ASP.NET Page Life Cycle
ASP.NET pages are event based
Event flow in ASPX pages
Page_Init: the page and controls are initialized
Page_Load: all the controls and page are loaded
Change events for controls are processed
Click events for controls are processed
Page_PreRender: page is about to render
Page_Unload: page is unloaded from memory

ASP Programming Models
Two types of programming models exist
ASPX page only: contains HTML, control tags, and code
Code behind model: ASPX file contains HTML and control tags, and a “code behind” file contains code
A true separation between code and content
One File Two files. (“code behind” model) Page.aspx Page.aspx Page.aspx.vb <Tags> + Code <Tags> Code

ASP.NET Features
Life made easy for developers
Excellent backward compatibility with classic ASP
Visual Studio designer support, rich server controls, and base class library support
Write code in the language of your choice
Call Microsoft Win32® APIs directly
Structured error handling
Great debugging and tracing support

ASP.NET Features (2)
Performance, scalability, and reliability
Compiled code means speed
Cache APIs to improve performance and scalability
Built-in support for WebFarms and WebGardens
Nonstop availability and protection against deadlocks, memory leaks, and so on

ASP.NET Features (3)
Easy deployment
X-copy deployment
Dynamic updates without interrupting the service
No more registry! — u se XML-based configuration files
New application models
Develop mobile Internet applications with ease
Built-in support to use XML WebServices
More control with the new security model
Flexible session state management
Many other new features

Core Object Changes
Request object changes:
Request(item) , Request.QueryString(item) , and Request.Form(item) now return a name value collection
In classic ASP, they return an array of strings
Use Response.Write with caution
It will output results at the top of the page before the <HTML> tag
Instead:
Use server controls (placeholder)
Use <% %> tags if you want the output to appear in the right place
Each of the core objects now have many new properties and methods.
There are some new objects available
For example: cache, user and trace

Structural Changes
One page – one language
No mixing of languages in single page
A page can have only one server-side Form tag and it must submit to the same page
An ASPX page may contain:
Directives: <%@ Directive %>
Server controls: <tag runat=server>
Code blocks: <script runat=server>
Data binding expressions: <%# %>
Server-side comments: <%-- --%>
Server-side includes: 
Render code: <%= %> and <% %>

Structural Changes (2)
Code block – related changes
You cannot declare functions inside <% %> tags
Declare all your functions and variables inside the server-side <SCRIPT> blocks
<Script runat=“server” language=“vb”>
dim gVar as String ‘Page level variable
private sub MySubRoutine()
Label1.Text = gVar
End Sub
</Script >

No Render functions permited
Change:
<% MyRenderFunction
Sub MyRenderFunction() %>
<h1> Hi there! </h1>
<%end sub%>
To:
<% Call MyRenderFunction()%>
<script runat=“server” language=“vb”>
Response.Write(“Hi there!”)
</script>

New page directives
In ASP, directives had to be at the top of the page, but you do not have to do this anymore
You can now have multiple directives on the same page
Sample page directive:
<%@ Page Language="VB" ContentType="text/xml" %>
See the documents on new page directives

Application Configuration Changes
ASP.NET application settings are stored in XML configuration files
Types of configuration files
Machine.config
Contains machine-wide settings
Web.Config
Contains project/application-wide settings
Easy programmatic access to the data in these files
Some of the settings in the IIS snap-in are ignored
For example: application protection level, session state

Session Management Changes
New session state storage mechanisms
InProc – session data stored on local computer (fastest)
StateServer – session data stored in a state service that can be located anywhere; ideal for WebFarms (faster)
SQLServer – session data stored in Microsoft SQL Server™ (fast)
Off – disable session state
Session state can be configured using <sessionState> section
Can store COM components in session only in InProc
Can store managed components in any session state modes

Security Related Changes
The IIS part of the security remains same
New robust and flexible security model is based on the security sections in the configuration files
New authentication modes
Windows: uses Windows Authentication
Forms: uses cookie-based custom logon forms
Passport: uses the Microsoft .NET Passport Service
None: no authentication
Authorization modes permit you to control access to resources:
File authorization
URL authorization
Permit and deny users access to the application

Migrating VBScript to Visual Basic .NET
No VBScript in ASP.NET — it’s all Microsoft Visual Basic® .NET!
Changing the file name extension to .aspx is the first step
Visual Basic language changes
Option Explicit is now the default
No more “variant” type — use type “Object”
Method and function calls with parameters now require parenthesis, so change:
<% Response.Write “Hi” %> to <% Response.Write (“Hi”) %>
By default, arguments are passed by value
Arrays are now zero based

Visual Basic Language Changes
Let and Set are not supported, so change:
Set MyObj1 = MyObj2 to MyObj1 = MyObj2
No more default properties (except for indexed properties), so change:
MyString as string = Textbox1 to MyString as string = Textbox.Text
Integer data type is now 32 bits and a Long data type is 64 bits
Use structured error handling (try catch block) instead of On Error (On Error still works)
Must cast data types explicitly:
Response.Write (“Count=“ & CStr(MyCount))
or Response.Write(“Count=“ & CType(MyCount, String))

Visual Basic Language Changes (2)
Must have spaces around “&” while doing string concatenation, so change:
x = str1&str2
to x = str1 & str2
Property Get, Property Set, and Property Let are not supported anymore, so instead use:
Public Property MyCount as Integer
Get
MyCount = InternalValue
End Get
Set
InternalValue = value
End Set
End Property

Migrating JScript to JScript .NET
Start by changing the file name extension to .aspx
Declare your variables explicitly
Microsoft JScript® .NET language changes
You can now pass variables by reference
“ expando” modifier available to extend user-defined objects
Can use COM components directly from JScript .NET
Server Object’s methods are case sensitive
The Arguments object is not available — use a parameter array instead
Functions cannot be redefined
For Large pages, move function/method code out of <% %> blocks to <Script runat=“server”> blocks

Migrating Applications that Use COM Components
COM related changes:
ASP.NET uses MTA instead of STA
Pages with STA components may or may not perform well
Early binding is preferred in ASP.NET
Cannot use ASPCOMPAT with WebServices
COM Interop
Can use all your former COM components in ASP.NET
Use ASPCOMPAT keyword if you plan to use existing STA components in ASP.NET
Use ASPCOMPAT only when using STA objects or when your COM objects access ASP intrinsic objects

COM Objects Migration — FAQ
What if the page contains both MTA and STA?
Use ASPCOMPAT
What if I have a middle tier containing COM objects?
Use horizontal or vertical migration strategies
What about the performance if I use existing COM objects?
Very little overhead if the method does substantial tasks
Significant overhead if the method does not do much

COM Objects Migration — FAQ (2)
What about deploying COM objects used in ASPX pages?
If you want to use Server.CreateObject, then there is no change
If you use early binding then use the PIA (Primary Interop Assembly) for the COM component and make sure you deploy the PIA on the target server
How can I use STA components from XML WebServices?
Register the component in COM+ and make sure you are running Windows 2000 SP2

Migrating Applications that Use Databases
Data access changes
ADO (through Interop) can be used, but Microsoft does not recommend it
ADO and ADO.NET are quite different
ADO.NET is not exactly backward compatible
Three main objects in ADO.NET: DataSet, DataReader, and DataAdapter
Two built-in managed data providers: SQLClient and OLEDB
Built-in designer support for ADO.NET objects in Visual Studio .NET

Migrating Applications that Use Databases (2)
Strategies
Rewrite ADO code in ADO.NET instead of migrating
Keep ADO code as a short term approach
If you use ADO code in ASP pages, use Primary Interop Assembly for ADO on both the developer box and the server
If you need read-only data, use a DataReader

Data Access Migration — FAQ
What if my application has straight ADO code in ASP pages?
Use ASPCOMPAT to use the code as it is (may be slower)
Rewrite the data access code to use ADO.NET
What if my application has COM objects that use data access?
Use the ASPCOMPAT attribute (if component uses STA)
What if my database has no managed providers?
You can use OLEDB providers in ADO.NET
If there are no OLEDB providers, use ODBC managed provider

Data Access migration — FAQ (2)
What if I have a data access tier?
Make these objects call Web Services or managed components
Later on, modify the presentation layer to use only .NET middle tier
Do I have to package ADO Components during deployment?
Make sure your server has MDAC 2.6 installed
Make sure you also deploy the PIA for ADODB on the server

General Migration Strategy
Identify the parts of the application that you have to migrate
Plan very carefully and try to have minimal impact on the existing application during the migration
In a multi-tier scenario, take the horizontal or vertical approach
Horizontal – migrate the whole tier (middle/presentation) at the same time
Vertical – migrate some pages, some components, at the same time
Decide if you want to reuse existing COM components

General Migration Strategy (2)
Decide if you want to keep current ADO code for a while
Rename the file name extension from .asp to .aspx
Make the language-specific changes first
Make COM- and database-specific changes
Test, test, test

Migration Best Practices
General
If the application is relatively small, consider rewriting
If the application is very large, then plan carefully and migrate part by part
If you only want to make a syntactic port, then consider only ASPX pages (that is, not using the “code behind” model) and do not make unnecessary changes
You do not have to port the whole site at the same time
Consider migrating the slow/critical parts
Remember, you can run ASP and ASP.NET side-by-side
Try to migrate the read-only pages first
Write automated tools to do some tasks

Migration Best Practices (2)
Language related
Strongly type all the variables
If possible, convert all the On Error statements to try catch blocks
Remember that they may not be as easy as they look
Convert Include files into assemblies or user controls (.ascx)
Use call keyword for function calls and use parenthesis for function and subroutine calls
Identify default properties and replace them appropriately
Always use Option Explicit

Data access related
If you have a data access tier, move it into .NET
COM related
Always use early binding
Explicitly free resources from code
Project management related
Keep two code trees while migrating, and make sure to update both of them while adding changes to the existing Web site
First try to modify the existing code as it is
After you complete this, try to modify the application to use the advantages provided by .NET

Testing related
Update existing links to your Web site/pages because the file name extension is now .aspx
Use a link checker to check any broken links, images, paths, and so on
Test very well

ASP to ASP.NET Compatibility — FAQ
How can ASP and ASP.NET co-exist?
Because they have different file name extensions (.asp and .aspx)
Because they have different application settings (registry and config files)
Can they share session and application data?
No – w rite custom code or use third-party component
What about Global.asa in ASP.NET?
In ASP.NET, it is called as Global.asax

ASP to ASP.NET Compatibility — FAQ (2)
Can I use .NET components from ASP, and COM components from ASP.NET?
Yes – use CCW to call managed components from ASP
Yes – u se RCW to call COM components from ASP.NET
What about the anonymous account in ASP.NET?
Remains the same
What about the hosting process in ASP.NET?
ASP.NET applications run under ASPNET_WP.EXE
By default, ASP.NET worker process runs under an account called ASPNET

ASP to ASP.NET Compatibility — FAQ (3)
Do I need to write code for different browsers?
No – ASP.NET produces HTML 3.2 compliant output
Can I still use ADO from ASP.NET?
Yes – y ou can use ADO through Interop, but ADO.NET is preferred
What about Include files?
Can be used, but better to convert them to class libraries or user controls (.ascx) instead
Can I call ASP pages from ASPX and vice versa?
Yes

ASP.NET Resources
ASP.NET Quick Start Tutorials
Authentication in ASP.NET Security
ASP.NET Security
Session State in ASP.NET
ASP.NET Configuration
http://www.gotdotnet.com
http://www.asp.net
http://www.ibuyspy.com

Migration Resources
Migrating to ASP.NET: Key Considerations
Migrating ASP Pages to ASP.NET
Converting ASP to ASP.NET
Upgrading to Microsoft .NET on GotDotNet
Upgrading to .NET on MSDN
Upgrading from JScript to JScript .NET
Microsoft .NET/COM Migration and Interoperability
Q314775 , “INFO: Migrating Visual InterDev Design-Time Controls to ASP.NET”
.NET Migration Case Study

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Migration from ASP to ASP.NET

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