.NET Developer Tooling: The Roslyn Revolution | Patrick Smacchia


Unless you’ve been on holidays for the last week on an island without internet,  you’ve probably heard that Microsoft announced that Roslyn is now available as Open-Source.

Roslyn is the next C# and VB.NET compiler, developed with these languages. It is not just a compiler but also provides an extensive set of APIs to do plenty of interesting stuff on source code including, intellisense, refactoring, static analysis, semantic analysis… This paradigm is called Compiler as a service.

Until now (I mean until Roslyn will be integrated in VisualStudio) the offer proposed by Visual Studio concerning these areas was pretty limited. If you need more than basics (in other word if you are a seasoned pro .NET Developer that value its time) you are certainly using daily Jetbrains Resharper or DevExpress CodeRush. But with Roslyn finally becoming a reality, these two well established tools teams are facing a dilemma. To use Roslyn or to not use it??!

  • Don’t use Roslyn, and take the risk that the Roslyn revolution will challenge the leading position. Another risk, more subtle but it’ll be very noticeable, is that Visual Studio will host in-memory the Roslyn infrastructure. So not using Roslyn will result in asking users to host two compiler/analysis infrastructures in its VS process. This will have a crucial consequence on both memory-consumption and performance. Not using Roslyn is the choice of the R# team and I am worried a bit since I am a big fan of R#.
  • Do use Roslyn, and take the risk to spend a massive refactoring effort for at least one release cycle, effort that could be spent on new features to increase competitiveness. Also, while Roslyn have been developed by some of the smartest brains on earth, it might not be suitable for doing everything. R# developers are claiming that their solution-wide analysis is not really doable with Roslyn. But investing into such huge refactoring is the choice of the CodeRush team. One important advantage with relying on Roslyn is that CodeRush will have future language features almost for free. This can pay off over the long term.

While my preference goes today to R#, it is likely that in five years from now, there will be one leading tooling built upon Roslyn, to achieve all these goodies (refactoring, analysis…). Will it be:

  • A VisualStudio extension developed by Microsoft. I have no idea if such project exist but it’d make sense. At least a partial product must be actually developed I guess.  A partial product that is not trying to implement all what CodeRush or R# can do, but at least increase substantially the actual basics  provided by VS out-of-the-box today.
  • CodeRush
  • A VisualStudio extension developed by a third company, we haven’t heard about yet.

Also we must take account that CodeRush and R# are actually super-mature products. Both teams are taking high risks for the future and it is not clear that another product (developed by the VS team or another team) might one day achieve such level of maturity.

NDepend has never been meant to compete with CodeRush nor R#. Some few features overlap, but many NDepend users are also using CodeRush or R# (like me actually).

NDepend is super-optimized to do macro-analysis. It does check hundreds of solution-wide code rules per second, while CodeRush and R# can do solution-wide checks, but more like in a matter of minutes on real-world large code base.

CodeRush and R# are brilliant to achieve micro-analysis, like showing to the user within the code editor that something can be improved in a method body. NDepend touches some of these areas, but a tool like CodeRush or  R# prove to be invaluable to obtain smart advises in all situations. And they come with the wonder of refactoring.

NDepend offers the necessary ten-thousands foot perspective, in order to take the most relevant refactoring decisions, like about what to do to make a component more cohesive, more re-usable, less coupled, less spaghetti-like. CodeRush and R# are excellent to actually achieve the refactoring once a decision has been taken.

Also, NDepend lets write custom code rules through LINQ queries. I believe our API, for that matter, is close to optimal. For ruling that Base class should not use derivatives it is as easy as writing:

No need to create a VS project. No need to click a compile or run button. Result is well formatted, well browsable and live updated if the rule gets edited. Such rule is executed in a few milli-seconds, even against a very large code base. And could the syntax be more concise? (thanks LINQ, thanks fluent API).

In addition NDepend has many other useful features out-of-the-box including code visualization (matrix, graph, treemap), code diff/baseline, code trending, reporting, code metrics including code coverage, tons of smaller-scale facilities to perform all sorts of convenient action… and many others features are in the development pipe. None of them really overlap with what other tools offer.

I went through all this description to say: NDepend is living in its own niche-area. So far it cohabits gently with CodeRush and Resharper and it doesn’t consume much extra memory nor extra performance. My opinion is that NDepend will cohabit well with Roslyn, without the need to be rebuilt upon it. If you don’t really agree with this, we’d be glad to hear your stance.