Automating C# Coding Standards using StyleCop and FxCop
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Automating C# Coding Standards using StyleCop and FxCop

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As organizations grow they usually seek to build a set of coding standards to enforce uniformity and increase the maintainability of their code base. Unfortunately, this often creates a lot of churn ...

As organizations grow they usually seek to build a set of coding standards to enforce uniformity and increase the maintainability of their code base. Unfortunately, this often creates a lot of churn in the code review process for simple style issues. This presentation was a session I gave at St. Louis Day of .NET 2010 and talks about how to automate many of the coding standards using two readily available tools.

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    Automating C# Coding Standards using StyleCop and FxCop Automating C# Coding Standards using StyleCop and FxCop Presentation Transcript

      • James Hare – Application Architect, Scottrade
    • What are Coding Standards?
      • A set of rules or guidelines used when writing the source code of a computer program.
      • Generally dictates:
        • Safety mandates to avoid introducing errors.
        • Style mandates to increase maintainability.
        • Security mandates to avoid vulnerabilities.
        • Efficiency mandates to help increase performance.
      • Standards may be enforced through code reviews or may simply be “suggestions”.
    • Standards: Like or Dislike?
    • But, Isn’t Programming Art?
      • This always has been an interesting point of contention.
        • On one extreme development can be thought of as a work of art and any source that reaches a logically correct result is acceptable and everything else is just “style.”
        • The other extreme believes that programming is purely a mechanical process and there is only a limited number of correct answers.
        • Which is correct?
    • Reality Lies In Between
      • It may be more accurate to say developers are more like artisans (crafters) than artists, though containing elements of both.
        • An artist has a wide range of forms they can adhere to and much is dependent on the interpretation of the viewer.
        • In contrast, artisans tend to construct or design for a purpose, and while there are some elements of style in construction, if it fails to achieve its purpose effectively , it is a failure.
    • The “Art” of Sorting
      • Take sorting, for example.
        • Both Bubble sort and Quick sort are valid sorts on a set of data.
        • Bubble sort has a complexity of O(n 2 ) and Quick sort is O(n log n).
        • Assuming sorting 1 million elements and each check takes 1 µs, roughly this would be:
          • Bubble Sort: 11 days
          • Quick Sort: 19 seconds
        • Both sort data, but one is clearly more useful.
    • Standardizing an “Art”
      • While there are many ways to solve a given problem, there should be guidelines for effective construction.
      • These guidelines are similar to building codes used in building construction to ensure safety and quality.
      • These guidelines form the basis for coding standards and are best compiled from group consensus and industry best practices.
    • Enforcing Standards
      • Standards should be enforced to promote safety, efficiency, and maintainability.
      • Standards can be enforced through Code Reviews, but these tend to be applied with varying levels of adherence.
      • It’s much better to attempt to automate as much of your standards as possible so that the code is judged more objectively.
    • Benefits of Automation
      • Standards are applied objectively since only analyzes the source or assembly.
      • Just plain faster than trying to catch standards violations manually.
      • Code authors don’t feel personally attacked.
      • Frees more reviewer time since won’t have to waste as much time in code reviews.
      • Frees more time for developers since code spends less time and iterations in review.
    • Standards Automation Tools
      • There are two primary tools from Microsoft:
        • StyleCop – Analyzes source files to determine if source code is correctly formatted.
        • FxCop (Static Code Analysis) – Analyzes assemblies to determine if code is constructed safely and optimally.
      • These tools overlap in some of their base rules but both have their strengths.
      • Other third party and Microsoft tools exist, but beyond this presentation’s scope.
    • StyleCop
      • Analyzes source files and not compiled code.
      • Great for checking elements such as:
        • Spacing
        • Comments
        • File composition
        • Naming
      • Cannot easily check type hierarchies or program structure.
      • Available at http://stylecop.codeplex.com/
    • Configuring StyleCop
      • If you have StyleCop installed, you can have Settings.StyleCop files for each project if you want to vary styles per project.
      • Will take the first Settings.StyleCop file it finds from working directory on up the path.
      • Default will be the Settings.StyleCop file in c:program filesMicrosoft StyleCop…
      • Various configurations can make harder to enforce uniform rules, though, so use with caution.
    • Configuring StyleCop
      • You can configure which base rules you want active by using StyleCopSettingsEditor.exe.
      • Let’s take a minute to look at the rules…
    • Configuring StyleCop
      • You can also get to StyleCop settings in Visual Studio directly by right-clicking a project.
      • This creates local copy of rules, use cautiously.
    • Running StyleCop
      • You can run StyleCop from VS or MSBuild.
      • Has no native command-line interface, but one exists at sourceforge called StyleCopCmd .
    • StyleCop Results
      • Shows in Error List window, can turn on “Warnings as Errors” in VS if you want to break builds on violations.
    • Suppressing a Rule
      • Most rules are good all the time, sometimes not.
    • On Suppressing Rules
      • It’s better to keep a rule even if it only applies 95% of the time and force developers to suppress the rule for the one-off exceptions.
      • This puts a SuppressMessage attribute in code which must be justified and prevents viewing the exception to the rule as a precedent for ignoring the rule.
      • If code reviewer disagrees, can be debated.
      • Turning off rules should be avoided unless the rule is invalid most or all of the time.
    • Custom StyleCop Rules
      • StyleCop rules are fairly easy to write.
      • Create class library that references the StyleCop assemblies:
        • Located in c:program filesMicrosoft StyleCop…
          • Microsoft.StyleCop.dll
          • Microsoft.StyleCop.Csharp.dll
      • Add a CS (C# source file) for new analyzer.
      • Add an XML file for rule configuration.
    • Custom StyleCop Rules
      • In the CS file, create an analyzer that inherits from SourceAnalyzer and has class attribute also named SourceAnalyzer for C# files.s
    • Custom StyleCop Rules
      • In the CS file, override AnalyzeDocument and perform your checks.
    • Custom StyleCop Rules
      • When you see your violation, call the method AddViolation and give it a rule name and args:
    • Custom Style Cop Rules
      • Then, in the XML file, define the rule and message. Make sure XML file has same name as class name and is Embedded Resource.
    • Custom StyleCop Rules
      • Then, build the custom assembly.
      • Place custom assembly in:
        • C:Program FilesMicrosoft StyleCop …
      • You should now see custom rules in the StyleCopSettingsEditor.
      • If you don’t see custom rules, check that the XML file:
        • Is an embedded resource
        • Has same filename as the class name (minus extensions)
      • Let’s look at the code more closely…
    • StyleCop for ReSharper
      • JetBrains’s ReSharper is an Visual Studio IDE plug-in that adds a lot of refactoring and aids.
      • StyleCop for ReSharper is a ReSharper plug-in that allows for dynamic checking of StyleCop rules as you type.
      • Will highlight rule violations with squiggle just like other ReSharper hints.
      • http://stylecopforresharper.codeplex.com/
      • Let’s look at how this appears in the IDE.
    • FxCop (aka VS Code Analysis)
      • Great for checking elements such as:
        • Non-spacing style issues (naming, etc).
        • Code safety and performance issues
        • Type hierarchy issues
        • Analysis of database objects
      • Cannot check source style such as spacing.
      • Already baked into Visual Studio 2008/10.
      • Can also be used as a stand-alone.
    • Running FxCop Stand-Alone
      • Start  Programs  Microsoft FxCop
      • Create new project, add targets, and Analyze!
    • Running FxCop From Visual Studio
      • Right click on project or solution and choose Run Code Analysis:
      • Let’s look at an example analysis.
    • Suppressing FxCop Errors
      • Just like in StyleCop, you can suppress one-off exceptions to the rules.
      • Can insert manually or automatically from the error list in Visual Studio.
    • Custom FxCop Rules
      • Create a Class Library in Visual Studio.
      • Add references to FxCop assemblies:
        • From C:Program FilesMicrosoft FxCop…
          • FxCopCommon.dll
          • FxCopSdk.dll
          • Microsoft.Cci.dll
          • Microsoft.VisualStudio.CodeAnalysis
      • Add a CS file for the new rule.
      • Add an XML file for the rule definition.
    • Custom FxCop Rules
      • In CS file create class that inherits from BaseIntrospectionRule :
    • Custom FxCop Rules
      • In CS File, override Check to check rule.
    • Custom FxCop Rule
      • XML file is Embedded and contains rule detail:
      • Remember filename must be same as passed to base constructor of BaseIntrospectionRule.
    • Custom FxCop Rules
      • To use custom rule, use CTRL+R or Project  Add Rules in FxCop.
      • You can verify by clicking on rules tab:
    • Summary
      • Automating code standards can be very useful for getting rid of a lot of the “noise” in code reviews and allowing reviewers to concentrate on logic bugs.
      • Automated code standards take the personal side out of enforcing style, safety, and performance.
      • Custom rules can be used in FxCop and StyleCop to allow for your own rules.
    • Questions?
      • Blog:
        • http://www.BlackRabbitCoder.net
      • Email:
        • [email_address]
      • Twitter:
        • http://twitter.com/BlkRabbitCoder