Best Practices ForBest Practices ForApplication DevelopmentApplication Development

Steven Wilssens & Jelle DruytsSteven Wilssens & Jelle DruytsCompuware .NET ConsultantsCompuware .NET Consultants

http://steven.wilssens.nethttp://steven.wilssens.nethttp://jelle.druyts.nethttp://jelle.druyts.net

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GoalsGoals

Write better codeDocument your codeApply design patterns in your codeFeel confident about your code

Be proud of your code

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AgendaAgenda

Developing CodeDocumenting CodeDesigning CodeTesting CodeBuilding Code

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Developing CodeDeveloping Code

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Exception HandlingException Handling

Handle exceptions consistently throughout your applicationMake exception handling code simpleBest practices:

Don't disclose security sensitive information to remote callersAdd context to exceptions by wrapping or replacing exceptionsLog and monitor all exceptions that occur

Developing CodeDeveloping Code

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LoggingLogging

Log business and operations data for runtime application monitoringMake logging code simpleBest practices:

Provide tracing to support production debuggingProvide auditing for increased securityChange logging settings through configuration

Which messages go where (file, event log, email, ...)How the messages are formatted (templates)When to log (information, warning, error, critical)

Developing CodeDeveloping Code

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Data AccessData Access

Read and write to commonly used databases in a simple and efficient wayMake data access code simpleBest practices:

Perform multiple updates within one transactionHandle different database providers transparently Separate logical from physical databasesChange connection settings through configuration

Provider type (SQL Server, Oracle, OLE-DB, ODBC, ...)Connection string

Developing CodeDeveloping Code

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CachingCaching

Eliminate expensive data retrieval by keeping a local copyMake caching code simpleBest practices:

Provide different cache invalidation mechanisms (absolute time, sliding time, file change, database change, ...)Provide different cache stores (in-memory, database)Use a local cache for offline operations on disconnected smart clientsDon't be afraid to use the ASP.NET cache anywhere for non-persistent storage (even in Windows Forms)

Developing CodeDeveloping Code

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CryptographyCryptography

Encrypt or hash sensitive information before persisting it; decrypt or compare when reading it backMake cryptography code simpleBest practices:

Never store passwords directly, only hash valuesOnly decrypt data if absolutely necessary (use a hash where possible)Use symmetric keys to encrypt and decrypt data across multiple machinesUse Windows DPAPI for cryptography on a single machine without using keys

Developing CodeDeveloping Code

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SecuritySecurity

Authenticate and authorize users using one or more security systemsMake security code simpleBest practices:

Use an authentication system to see if a user can access a systemUse an authorization system to see if a user can perform a certain taskCache authentication or authorization data for the duration of a logon session

Developing CodeDeveloping Code

Enterprise Library 2.0Enterprise Library 2.0

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Enterprise Library 2.0Enterprise Library 2.0

Set of reusable components from MicrosoftConsistentExtensibleEasy to useIntegrated

Source code you compile yourselfFreeNot a Microsoft productTested through many unit tests

Use only the blocks you needVisual configuration tool

Developing CodeDeveloping Code

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Key Changes From 1.xKey Changes From 1.x

Configuration Application Block no longer exists

Configuration now built on System.ConfigurationLogging Application Block

Much improved flexibility and performanceData Access Application Block

Simpler and much more powerfulSupports SQL Server, Oracle, OLE-DB, ODBC or any other managed provider

Security Application Block Most of it deprecated in favor of .NET’s Membership and Profile features

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Data Data AccessAccess LoggingLogging

Enterprise Library 2.0 BlocksEnterprise Library 2.0 Blocks

Plug-inConfigConfig

Helpers Helpers & Design& Design

Instrumen-Instrumen-tationtation

ObjectObjectBuilderBuilder

CryptographyCryptography

Core

Block DependencyOptional ProviderDependency

Developing CodeDeveloping Code

SecuritySecurity

CachingCaching

ExceptionExceptionHandlingHandling

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Enterprise Library 2.0Enterprise Library 2.0

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Documenting CodeDocumenting Code

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Why?Why?

Your code is not self-documentingUndocumented code is untestable codeEasier to plan next versionEasier to return laterBrings new team members quickly up to speedCreates happy customers

Documenting CodeDocumenting Code

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How?How?

Put XML comments on your codeDocument all public and protected membersLearn and use the XML tags

Write additional contentUser's guide & Known issuesInstallation & Configuration guide

Generate documentationCHM, HTML, HxS, ...

Documenting CodeDocumenting Code

/// <summary>/// Write a new log entry to the default category./// </summary>/// <param name="message">Message body to log.</param>public static void Write(object message) { ... }

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Documentation ToolsDocumentation Tools

CR_DocumentorNDoc (being updated for .NET 2.0)

Documenting CodeDocumenting Code

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Designing CodeDesigning Code

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Command Pattern and Command Pattern and Enterprise Library 2.0Enterprise Library 2.0

Designing CodeDesigning Code

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Testing CodeTesting Code

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TestabilityTestability

Allow unit testing of major part of applicationTests must be deterministicTests must be automatedTests must be efficient (execute quickly)

Testing CodeTesting Code

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Dependency PrinciplesDependency Principles

Communicate with interfaces or base classesSeparate interface definitions from implementationsUse dependency injection to late-bind objectsExternalize environment dependenciesExternalize non-deterministic behaviorExternalize timing behavior

Testing CodeTesting Code

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Unit TestingUnit Testing .NET .NET

NUnitVisual Studio Test

Testing CodeTesting Code

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General PrinciplesGeneral Principles

Test cases must be independentReproduce bugs as test casesTest only public membersPlace tests in separate projectsHave a test project per test targetUse source control on test projects

Testing CodeTesting Code

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Test-Driven DevelopmentTest-Driven Development

Write unit tests before or in parallel with production codeUnit tests help define the systemUnit tests are debugging driversDevelopers write the tests”It’s better to write and run incomplete tests than not to run complete tests”

Testing CodeTesting Code

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Test Driven DevelopmentTest Driven Development

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Code Coverage BasicsCode Coverage Basics

Records which parts of an application's code is being exercised by a test suite

Testing CodeTesting Code

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Code Coverage BCode Coverage Best est PracticesPractices

Use code coverage to monitor your tests' effectiveness

Project managers can aggregate results as a project status indicatorTeam members can analyze source for specific missed lines of code

Set a high, but realistic target

Testing CodeTesting Code

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Code Coverage PCode Coverage Pitfallsitfalls

Best quantifiable measureDoesn’t say a lot about quality of testsBeware of developer shortcuts

Testing CodeTesting Code

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Code CoverageCode Coverage

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Building CodeBuilding Code

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Daily Build DefinitionDaily Build Definition

Daily builds are the results of a fully automated process which, by using source code, compiles, validates, and packages a software solution

Daily builds don’t have to run each day, as long as they run frequently

Building CodeBuilding Code

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Introducing Daily BuildsIntroducing Daily Builds

”The build is the heartbeat. If there ain’t no heartbeat, it’s dead!”Must be fully automatedDifficult to doNo excuse for not doing daily builds: The more complex your system is, the more you need it

Building CodeBuilding Code

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Daily Build BenefitsDaily Build Benefits

State of project becomes more transparentYou always have a product that can potentially shipCurrent test target always availableAnti-surprise deviceReduces overall integration effort

Building CodeBuilding Code

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Team BuildTeam Build

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Key PointsKey Points

Developing CodeUse Enterprise Library 2.0

Documenting CodeUse XML comments and NDoc to generate CHM files

Designing CodeCommand Pattern can be used to integrate many enterprise library 2.0 features

Testing CodeYou can take a pragmatic or a formal approach to unit testing

Building CodeUse build verification tests to verify soundness of a build

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Enterprise Library 2.0http://msdn.microsoft.com/practiceshttp://practices.gotdotnet.com/projects/entlib

Code DocumentationXML Comments Quick Reference

http://jelle.druyts.net/2005/01/16/XMLCommentsQuickReference.aspx

NDochttp://ndoc.sourceforge.net/

CR_Documentorhttp://www.paraesthesia.com/blog/comments.php?id=701_0_1_0_C

Command Patternhttp://steven.wilssens.net/

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Thank You!Thank You!

Thanks for your attention

We'll be happy to answer all your questions

Right after the sessionCompuware BoothCommunity Booth: Ask-The-Experts VISUG Booth

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