ISV Community DayISV Community DayBest Practice

Per AhlbergDeveloper EvangelistDeveloper & Platform EvangelismMicrosoft Sweden

AgendaAgenda

General Best Practices COM Components best practice Data layer best practice ASP to ASP.NET Best Practices

General Migration StrategyGeneral 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

Migration Best PracticesMigration Best Practices

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

Migration Best PracticesMigration Best Practices 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

Migrating Applications that Use Migrating Applications that Use COM ComponentsCOM 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 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

Migration Best PracticesMigration Best Practices

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 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

Remove Microsoft.VisualBasic namespace

ADO ADO ADO.NET ADO.NET

ADO evolves into ADO.NET

DataReaderDataReader

DataAdapterDataAdapter

DataSetDataSet

CommandCommand

ConnectionConnection

RecordSetRecordSet

CommandCommand

ConnectionConnection

Migrating Applications that Use Migrating Applications that Use DatabasesDatabases 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 Built-in designer support for ADO.NET objects

in Visual Studio .NET

Migrating Applications that Use Migrating Applications that Use DatabasesDatabases 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

High level strategies: Replace VB6 components directly by VB.NET

components, horizontally or vertically Let ASP.NET call Web Services that encapsulate VB6

business components, then migrate these as needed to .Net

Replacing VB6 components directlyReplacing VB6 components directly

Your .NET code can talk directly to VB6 COM code, but...

If your VB6 business components require passing variants, write strongly-typed “inbetween” .Net components (adapters) ASP.NET talks to the inbetween components The inbetween components talk to the

existing VB6 components and perform data conversion to strong types

VB6.MyWeakComponent:

Public Function UpdatedData(Name As String, Age As Variant, MyDataArray As Variant) As Variant

Public Function UpdatedData(Name As String, Age As Variant, MyDataArray As Variant) As Variant

VBNet.MyStrongComponent:

Public Function UpdatedData(Name As String, Age As Integer, MyDataArray As Array Of Single) As Double

Public Function UpdatedData(Name As String, Age As Integer, MyDataArray As Array Of Single) As Double

In version 1, VBNet.MyStrongComponent calls VB6.MyWeakComponent and performs type conversion as needed

Replacing VB6 components directlyReplacing VB6 components directly

.NET.NET

VB6 comp

.NET.NET

VB.NETcomp

VB6 comp

Before After

Business Business logiclogic

Adapter Adapter logiclogic

Business Business logiclogic

Replacing VB6 components directlyReplacing VB6 components directly

By building these adapter components, .NET code can be fully typed as needed and the UI can be completely replaced

As a next step, you can change the VB.NET Business components to replace the VB6 business components You have now replaced your Business logic layer

Replacing VB6 components directlyReplacing VB6 components directly

Migrating Applications that Use Migrating Applications that Use COM ComponentsCOM Components COM related changes:

.NET uses MTA instead of STA ASP.NET Pages with STA components

may or may not perform well Early binding is preferred in .NET Cannot use ASPCOMPAT with WebServices

COM Interop Can use all your former COM components 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

If your original VB6 code returned ADO Recordsets, it is best to make the VB.NET versions return ADO.NET DataSets instead: Convert ADO Recordsets to ADO.NET DataSets

as needed in the Business layer ASP.NET then works only with ADO.NET Many ASP.NET Web Controls work with

DataSets ADO.NET DataSets can be marshalled

efficiently even across physical tiers

Replacing components layer by Replacing components layer by layerlayer

Replacing components layer by Replacing components layer by layerlayer Later, migrate the Data layer and make it return

ADO.NET DataSets instead of ADO Recordsets Remove the RecordsetDataSet conversion code

from the Business components For components you can’t migrate, stick to COM

Interop

Replacing components layer by Replacing components layer by layerlayer What about transactional integrity and

security context? In VB6 under Windows NT: MTS In VB6 under Windows 2000: COM+ In .NET: COM+

Replacing components layer by Replacing components layer by layerlayer Derive your façade components from the

ServicedComponent base class to use COM+ transactions and security Interestingly, the components that a

ServicedComponent calls don’t need to be serviced – they use the caller’s context!

Use attributes to control configuration Best to put them in the AssemblyInfo.vb file

Register your façade’s assembly in the GAC

Wrapping VB6 components Wrapping VB6 components by .NET Web Servicesby .NET Web Services Alternatively, start by having your

ASP.NET pages consume .NET Web Services that wrap the VB6 components

This allows for easy separation in physical tiers (dedicated application servers) as well as logical tiers

A better option to separate in physical tiers is to use .Net Remoting

If you need transactional integrity across physical tiers, use Serviced Components

.NET.NET

VB6 comp

.NET.NET

VB6 comp

Before After

Business Business logiclogic

Adapter Adapter logiclogic

Business Business logiclogic

ASP.NET ASP.NET Web Web

ServiceService

Physical boundaryPhysical boundary

Wrapping VB6 components Wrapping VB6 components by .NET Web Servicesby .NET Web Services

.NET.NET

VB6 comp

.NET.NET

VB.NETcomp

Before After

Business Business logiclogic

Wrapper Wrapper logiclogic

Business Business logiclogic

ASP.NET ASP.NET Web Web

ServiceService

Physical boundaryPhysical boundary

Wrapping VB6 components Wrapping VB6 components by .NET Web Servicesby .NET Web Services

Web Services use open standards You can open your business logic to other

applications as well, over the Internet, if you want But be careful: Web Services can be transactional,

but only as the transactional root You can’t combine more than 1 Web Service into a

transaction

Wrapping VB6 components Wrapping VB6 components by .NET Web Servicesby .NET Web Services

ASPASP

VB6 comp

.NET.NET

VB6 comp

Replacing VB6 components Replacing VB6 components indirectly with Remotingindirectly with Remoting

Before After

Business Business logiclogic

Business Business logiclogic

Physical boundaryPhysical boundary

VB.NETcomp

Adapter Adapter logiclogic

Replacing VB6 components Replacing VB6 components indirectly with Remotingindirectly with Remoting Remoting is “.Net DCOM” Better performance than with Web Services

We measured TCP binary remoting to provide 200%-300% the speed of web services with SOAP

Calling a component through remoting does not maintain transactional integrity and security context, however

Remoting only works from .Net to .Net

COM Best PracticeCOM Best Practice

Use Primary Interop Assemblies Produced by COM API owner May be modified for correctness or managed client

friendliness Recognized by Visual Studio.NET Ensure consistent identity for Interop types

Visual Studio ships with PIAs C:\Program Files\Microsoft.NET\Primary Interop Assemblies

Office 2003 PIAs also available http://msdn.microsoft.com/library/default.asp?url

=/downloads/list/office.asp

Contain structured data: ShoppingCart, UserProfile, Catalog Are classes that inherit from DataSet Inherit all DataSet’s standard

functionalities Automatically copyable, mergable,

serializable, ... Can be autogenerated by the .NET

framework’s xsd.exe tool

Typed DataSetsTyped DataSets

ds.Tables(“Customers”).Rows(0).Columns(“Name”) _= “Steve Ballmer”

ds.Tables(“Customers”).Rows(0).Columns(“Name”) _= “Steve Ballmer”

UntypedUntyped

ds.Customers(0).Name = “Steve Ballmer”ds.Customers(0).Name = “Steve Ballmer”

TypedTyped

Typed DataSetsTyped DataSets

Add properties specific to the structured data:

IntelliSense!

They don’t solve all your data modeling needs: You still have to write code to populate them Marshalling serializable objects (such as DataSets)

rather than plain strings (such as XML strings) requires more CPU

... but the simplicity and power of using DataSets more than makes up for it

See IBuySpy reference implementation

Typed DataSetsTyped DataSets

ASP to ASP.NET Best PracticesASP to ASP.NET 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

Finally Best Practices...Finally Best Practices...

Use Enterprise Templates that implement and force good coding practices

Use .Net’s standard naming conventions Use structured exception handling Use Typed DataSets rather than “generic”

DataSets whenever possible It’s not the ultimate panacea but it’s better

than generic DataSets for strong typing and IntelliSense