SonarLint Visual Studio Extension / C# Linter

I’m currently working on a legacy code base that’s not a shining example of clean code and best practices.

I try to improve the code as I work, a careful balancing act where I do my best not to impact productivity by spending too much time on refactoring and reformatting.

To help me with this task I decided to look into linters. Note that I’m not using ReSharper which would help with code quality, but that’s another story.

I tried StyleCop, but with the default settings I just wasn’t impressed. Many rules are in my opinion needlessly restrictive. It also seemed to simply dump more than a thousand warnings in the error window.

I tried SonarLint next and I must say I was thoroughly impressed. Though the errors are also sent to the error window they are also shown inline in the file. The parsing by SonarLint was fast and running the Visual Studio extension only had a very small impact on performance even while working with a solution containing thousands of files and hundreds of thousands of lines of codes.

While I haven’t run ReSharper in years, performance was one of the two reasons I stopped using it. On large solutions like the one I’m currently working with, it would slow everything down to a crawl, even when disabling solution-wide analysis.

SonarLint isn’t exactly what I was expecting it to be. I thought it would be more for style guidelines but it has instead given me deeper insights. I’m specifically referring to my last two examples.

Things like needlessly nested if statements:

if (FirstProperty == false) 
{
    if (NeedlesslyDeeplyScoped == true)
    { }
}

Using a Count() instead of an Any:

if (files.Count(f => f.IsDeleted) > 0)
// to
if (files.Any(f => f.IsDeleted))

To foreach statements that can run on null variables:

List<Foo> myCollection = null;

if (IsWeatherRainy) 
{
    myCollection = new List<Foo>();
    // add stuff
}

// myColllection null on at least one execution path
foreach (var item in myCollection)

Or overlapping method signatures with optional parameters that can’t be used:

// This method's signature overlaps the second one
// and the default parameter value can't be used
public File GetFile(bool firstParam, 
                    bool secondParam = false)
{
    return new File();
}

public TestFile GetFile(bool firstParam)
{
    return new TestFile();
}

This last one having been found three times in a single file.

SonarLint is available on the Visual Studio marketplace. It’s free and open source with a repository on GitHub. It’s created by a company that also sells a similar product (though geared towards CI / Build servers) but I haven’t found any downsides to using the free Visual Studio Extension.

By the way, I haven’t been asked to write this by the company that makes SonarLint.

One thought on “SonarLint Visual Studio Extension / C# Linter

  1. > I try to improve the code as I work, a careful balancing act where I do my best not to impact productivity by spending too much time on refactoring and reformatting.

    I tried the same at my previous company, and I’m not sure I did it right, despite my best efforts and intentions. After all, the legacy code was working (= in production), and fixing quality issues without extensive automated tests was either risky, or creating the necessary tests was expensive (developer time). The water leak paradigm proposed by SonarSource was an eye-opener for me, I recommend to check it out if you haven’t done already.
    https://blog.sonarsource.com/water-leak-changes-the-game-for-technical-debt-management/

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