Improve your .NET code quality with NDepend

Quickly assess your .NET code compliance with .NET Standard

Yesterday evening I had an interesting discussion about the feasibility of migrating parts of the NDepend code to .NET Standard to ultimately run it on .NET Core. We’re not yet there but this might make sense to run at least the code analysis on non Windows platform, especially for NDepend clones CppDepend (for C++), JArchitect (for Java) and others to come.

Then I went to sleep (as every developers know the brain is coding hard while sleeping), then this morning I went for an early morning jogging and it stroke me: NDepend is the perfect tool to  assess some .NET code compliance to .NET Standard, or to any other libraries actually! As soon on my machine I did a proof of concept in a few minutes, then spent half an hour to fix an unexpected difficulty (explained below) and then it worked.

The key is that .NET standard 2.0 types are all packet in a single assemblies netstandard.dll v2.0 that can be found under C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319 (on my machine). All these 2,334 types are actually type forward definitions and NDepend handles well this peculiarity. A quick analyze of netstandard.dll with NDepend with this quick code query makes it all clear: 

(Btw, I am sure that if you read this  you have an understanding of what is .NET Standard but if anything is still unclear, I invite you to read this great article by my friend Laurent Bugnion wrote 3 days ago A Brief History of .NET Standard)

.NET Standard Forwarded Types

Given that, what stoke me this morning is that to analyze some .NET code compliance to .NET Standard, I’d just have to include netstandard.dll in the list of my application assemblies and write a code query that  filters the dependencies the way I want. Of course to proof test this idea I wanted to explore the NDepend code base compliance to .NET Standard:

NetStandard assembly included in the NDepend assemblies to analyze

The code query was pretty straightforward to write. It is written in a way that:

  • it is easy to use to analyze compliance with any other library than .NET standard,
  • it is easy to explore the compliance and the non-compliance with a library in a comprehensive way, thanks to the NDepend code query result browsing facilities,
  • it is easy to refactor the query for querying more, for example below I refactor it to assess the usage of third-party non .NET Standard compliant code

The result looks like that and IMHO it is pretty interesting. For example we can see at a glance that NDepend.API is almost full compliant with .NET standard except for the usage of System.Drawing.Image (all the 1 type are the Image type actually) and for the usage of code contracts.

NDepend code base compliance with .NET standard

For a more intuitive assessment of the compliance to .NET Standard we can use the metric view, that highlights the code elements matched by the currently edited code query.

  • Unsurprisingly NDepend.UI is not compliant at all,
  • portions of NDepend.Core non compliant to .NET Standard are well defined (and I know it is mostly because of some UI code here too, that we consider Core because it is re-usable in a variety of situations).

With this information it’d be much easier to plan a major refactoring to segregate .NET standard compliant code from the non-compliant one, especially to anticipate hot spots that will be painful to refactor.

Treemap view of the compliance with .NET Standard

A quick word about the unexpected difficulty I stumbled on. Since netstandard.dll contains only type forward definitions, it doesn’t contain nested type. Concretely it contains List<T> but not List<T>+Enumerator (that is also part of the formal .NET Standard). Of course we don’t want to flag methods that use List<T>+Enumerator as non-compliant. To see the way we solved that, have a look at the tricky part in the code code query related to: allNetStandardNestedTypes

The code query to assess compliancy can be refactored at whim. For example I found it interesting to see which non-compliant third-party code elements were the most used. So I refactored the query this way:

Without surprise UI code that is non .NET Standard compliant popups first:

.NET Standard non-compliant third-party code usage

There is no limit to refactor this query to your own need, like assessing usage of non-compliant code — except UI code– for example, or assessing the usage of code non compliant to ASP.NET Core 2 (by changing the library).

Hope you’ll find this content useful to plan your migration to .NET Core and .NET Standard!

Checking DDD Ubiquitous Language with NDepend

Since NDepend version 2018.1, the tool proposes a default rule to check Domain Driven Design (DDD) Ubiquitous Language validity.

DDD Ubiquitous Language

Let’s quote Martin Fowler on Ubiquitous Language:

Ubiquitous Language is the term Eric Evans uses in Domain Driven Design for the practice of building up a common, rigorous language between developers and users. This language should be based on the Domain Model used in the software – hence the need for it to be rigorous, since software doesn’t cope well with ambiguity.

Evans makes clear that using the ubiquitous language between in conversations with domain experts is an important part of testing it, and hence the domain model. He also stresses that the language (and model) should evolve as the team’s understanding of the domain grows.

–Martin Fowler

Eric Evans coined the term DDD, let’s quote him:

By using the model-based language pervasively and not being satisfied until it flows, we approach a model that is complete and comprehensible, made up of simple elements that combine to express complex ideas.

Domain experts should object to terms or structures that are awkward or inadequate to convey domain understanding; developers should watch for ambiguity or inconsistency that will trip up design.

–Eric Evans

See below a sample of ubiquitous language usage in the real-world. We end up with clean and readable code:

The TrainTrain Code Base

To explain and demonstrate the rule, we’ll conduct our experiment on the TrainTrain code base.

This OSS code base has been developed by Bruno Boucard and Thomas Pierrain from 42Skillz, a French consultancy company specialized in DDD and developers coaching. TrainTrain has been developed in order to illustrate concretely most of DDD concepts (including Ubiquitous Language) in a session named How To Distill The Core Domain From Your Legacy App (Live Coding). In this session, a legacy version of the code is live-refactored to a DDD-compliant version. It has been performed both at Explore DDD 2017 (Denver, Sept 2017) and DDD Europe 2018 (Amsterdam, Jan 2018).

We worked with Bruno and Thomas to develop this first rule related to DDD and we expect that more rules will follow from this collaboration.

The Rule

See below the full source code of the new rule named DDD ubiquitous language check that can be found in the rule group Naming Convention. This rule is disabled by default because before using it, the user must customize both:

  • The core domain namespace name (by default set to “TrainTrain.Domain”)
  • The vocabulary list

The idea is to centralize in this rule source code the vocabulary. The rule then checks that all code elements defined in the core domain namespace are named with one or several terms found in the vocabulary list. Code elements checked include classes, enumerations, structures, interfaces, methods, properties and fields. If a term needs to be used both with singular and plural forms, both forms need to be mentioned, like Seat and Seats for example.

The NDepend rule system makes easy to modify the source code of an existing rule. There is no Visual Studio project to create and store, no NuGet package to reference, no assembly to compile, version and maintain, no integration. Just textual edition with code completion, API documentation and live result while editing, and then Ctrl+S, that’s it. As a consequence, the NDepend rule system is well suited to implement such rule that must be customized with some user data before usage.

Notice that this rule relies on the new NDepend API method ExtensionMethodsString.GetWord(this string identifier). This method extracts words from code identifiers. For example from the field identifier _seatsRequestedCount it extracts the 3 words seats, Requested, Count. To be compliant with the vocabulary list, we then set the first char to upper, for example seats becomes Seats.

Running the Rule

See below a screenshot on running this rule on a TrainTrain version. An issue is spotted on a core domain class named TreasholdCapacity. Both words are reported in the column wordsNotInVocabulary because both words are not in the vocabulary list. Moreover the word Treashold has a typo. At this point, to fix this issue:

  • either this class should be renamed with existing core domain vocabulary words
  • either these words should be added to the vocabulary list (with the typo fix)


DDD is nowadays a popular concept. We are proud to innovate with a static analysis code rule related to DDD. We have plans for more DDD related rules and we would like to hear both your feedback on using this rule, and your needs for more DDD related rules.


New .NET Core 2.1 and ASP.NET Core 2.1 APIs

.NET Core 2.1 and ASP.NET Core 2.1 Preview1 have just been released (see here the official announcement) and we are going to explore new APIs in this post. We’ll found out many of the new features announced in the .NET Core 2.1 Roadmap and ASP.NET Core 2.1 Roadmap on the MSDN blog.

We just released NDepend v2018.1 and we took a chance to support analysis of .NET Core 2.1 and ASP.NET Core 2.1 applications. NDepend is often deemed as the Swiss-Army Knife for .NET developers thanks to its code query language (CQLinq). CQLinq can be used to write code rules, quality gatestrend code metrics, explore dependencies or advanced code search. One thing CQLinq excels at is exploring the diff between two snapshots of a code base. Exploring new APIs is a sub-task of exploring what was changed. Let’s harness this capability to explore new .NET Core 2.1 APIs.

New .NET Core 2.1 Preview1 APIs

We could have downloaded sources files of both .NET Core 2.1.0 Preview1 and 2.0.0, recompile and then do the diff. Instead, since NDepend can analyze raw assemblies even without sources available, we compared assemblies in these two folders:

  • C:\Program Files\dotnet\shared\Microsoft.NETCore.App\2.1.0-preview1-26216-03
  • C:\Program Files\dotnet\shared\Microsoft.NETCore.App\2.0.5

Here is the CQLinq code query that lists all new public classes and types. It is also refined to match public members (methods and fields) of each new type in the result.

Find the whole list here .NET Core 2.1 new public classes. Here is a first glimpse in the screenshot below. We highlighted the new great Span<T> capability.

.NET Core 2.1 new classes

Not only new public classes list is interesting, but also new public methods added on existing public classes. This query does list these 1.500 methods:

Here also find a screenshot below and the whole list here: .NET Core 2.1 new public methods on existing public classes. For this screenshot we used the new Dark theme support of NDepend v2018.1.

.NET Core 2.1 new public methods

Interestingly enough let’s list new namespaces that contain at least one public type:

.NET Core 2.1 new public namespaces


New ASP.NET Core 2.1 Preview1 APIs

To analyze ASP.NET Core assemblies it was a bit more difficult than just comparing assemblies in 2 folders. ASP.NET Core assemblies are stored in NuGet packages so we did explore assemblies in the folder C:\Program Files\dotnet\sdk\NuGetFallbackFolder and then tinker a bit to get the wanted versions in both 2.1 and 2.0 cases.

Let’s use the same code query to match ASP.NET Core 2.1 new public classes :

ASP.NET Core 2.1 new public class

The same way here is the ASP.NET Core 2.1 new public methods on existing public classes :

ASP.NET Core 2.1 new public methods in existing public classes

And finally, here are the new ASP.NET Core 2.1 namespaces that contain at least one public classes.

ASP.NET Core 2.1 new namespaces



A problem with extension methods

We like extension methods. When named accordingly they can both make the caller code clearer, and isolate static methods from classes on which they operate.

But when using extension methods, breaking change can happen, and this risk is very concrete, it actually just happened to us.

Since 2012, NDepend.API proposes a generic Append() extension:

Two default rules use this extension method: Avoid namespaces dependency cycles and Avoid types initialization cycles

Last month, on Oct 17th 2017, Microsoft released .NET Framework v4.7.1 that implements .NET Standard 2.0. Around 200 .NET Standard 2.0 were missing in .NET Framewok v4.6.1, and one of those missing API is:

Within NDepend, rules, quality gates, trend metrics … basically everything, is a C# LINQ query stored as textual and compiled and executed on-the-fly. Since the compilation environment uses both namespaces NDepend.Helpers and System.Linq, when running NDepend on top of the .NET Framework v4.7.1, both Append() extension methods are visible. As a consequence, for each query calling the Append() method, the compiler fails with:

Hopefully a user notified us with this problem that we didn’t catch yet and we just released NDepend v2017.3.2 that fixes this problem Only one clean fix is possible to make it compatible with all .NET Framework versions: refactor all calls to the Append() extension method,  into a classic static method invocation, with an explanatory comment:

We expect support on this within the next weeks and months when more and more users will run the .NET Fx v4.7.1 while not changing their rules-set. There is no lesson learnt, this situation can happen and it happens rarely, this shouldn’t prevent you from declaring and calling extension methods. The more mature the frameworks you are relying on, the less likely it’ll happen.

Static analysis of .NET Core 2.0 applications

NDepend v2017.3 has just been released with major improvements. One of the most requested features, now available, is the support for analyzing .NET Core 2.0 and .NET Standard 2.0 projects. .NET Core and its main flavor, ASP.NET Core, represents a major evolution for the .NET platform. Let’s have a look at how NDepend is analyzing .NET Core code.

Resolving .NET Core third party assemblies

In this post I’ll analyze the OSS application ASP.NET Core / EntityFramework MusicStore hosted on github. From the Visual Studio solution file, NDepend is resolving the application assembly MusicStore.dll and also two test assemblies that we won’t analyze here. In the screenshot below, we can see that:

  • NDepend recognizes the .NET profile, .NET Core 2.0, for this application.
  • It resolves several folders on the machine that are related to .NET Core, especially NuGet package folders.
  • It resolves all 77 third-party assemblies referenced by MusicStore.dll. This is important since many code rules and other NDepend features take into account what the application code is using.

It is worth noticing that the .NET Core platform assemblies have high granularity. A simple website like MusicStore references no fewer than 77 assemblies. This is because the .NET Core framework is implemented through a few NuGet packages that each contain many assemblies. The idea is to release the application only with needed assemblies, in order to reduce the memory footprint.

.NET Core 2.0 third party assemblies granularity

NDepend v2017.3 has a new heuristic to resolve .NET Core assemblies. This heuristic is based on .deps.json files that contain the names of the NuGet packages referenced. Here we can see that 3 NuGet packages are referenced by MusicStore. From these package names, the heuristic will resolve third-party assemblies (in the NuGet store) referenced by the application assemblies (MusicStore.dll in our case).

NuGet packages referenced in .deps.json file

Analyzing .NET Standard assemblies

Let’s be clear that NDepend v2017.3 can also analyze .NET Standard assemblies. Interestingly enough, since .NET Standard 2.0, .NET Standard assemblies reference a unique assembly named netstandard.dll and found in C:\Users\[user]\.nuget\packages\NETStandard.Library\2.0.0\build\netstandard2.0\ref\netstandard.dll.

By decompiling this assembly, we can see that it doesn’t contain any implementation, but it does contain all types that are part of .NET Standard 2.0. This makes sense if we remember that .NET Standard is not an implementation, but is a set of APIs implemented by various .NET profiles, including .NET Core 2.0, the .NET Framework v4.6.1, Mono 5.4 and more.

Browsing how the application is using .NET Core

Let’s come back to the MusicStore application that references 77 assemblies. This assembly granularity makes it impractical to browse dependencies with the dependency graph, since this generates dozens of items. We can see that NDepend suggests viewing this graph as a dependency matrix instead.

NDepend Dependency Graph on an ASP.NET Core 2.0 project

The NDepend dependency matrix can scale seamlessly on a large number of items. The numbers in the cells also provide a good hint about the represented coupling. For example, here we can see that  22 members of the assembly Microsoft.EntityFrameworkCore.dll are used by 32 methods of the assembly MusicStore.dll, and a menu lets us dig into this coupling.

NDepend Dependency Matrix on an ASP.NET Core 2.0 project

Clicking the menu item Open this dependency shows a new dependency matrix where only members involved are kept (the 32 elements in column are using the 22 elements in rows). This way you can easily dig into which part of the application is using what.

NDepend Dependency Matrix on an ASP.NET Core 2.0 project

All NDepend features now work when analyzing .NET Core

We saw how to browse the structure of a .NET Core application, but let’s underline that all NDepend features now work when analyzing .NET Core applications. On the Dashboard we can see code quality metrics related to Quality Gates, Code Rules, Issues and Technical Debt.

NDepend Dashboard on an ASP.NET Core 2.0 project

Also, most of the default code rules have been improved to avoid reporting false positives on .NET Core projects.

NDepend code rules on an ASP.NET Core 2.0 project

We hope you’ll enjoy using all your favorite NDepend features on your .NET Core projects!

Migrating from HTTP to HTTPS in a IIS / ASP.NET environment

Google is urging more and more webmasters to move their sites to HTTPS for security reasons. We did this move last week for our IIS / ASP.NET website https://www.NDepend.com and we learned a few tricks along the way. Once you’ve done it once it becomes pretty straightforward, but getting the big picture and handling every detail well is not trivial. So I hope this post will be useful.

HTTPS and Google Analytics Referrals

One reason for moving to HTTPS is that Google Analytics referrals don’t work when the user comes from a HTTPS website. And since most of your referrers websites are likely to be already HTTPS, if you keep up with HTTP, your GAnalytics becomes blind.

Notice that once you’ve moved to HTTPS, you still won’t be able to track referrers that come from an HTTP url, which is annoying since most of the time you don’t have edit-access to these urls.

Getting the Certificate

You can get free certificates from LetsEncrypt.com, but they have a 3 month lease. The renewal process can certainly be automated, but instead we ordered a 2 year certificate from gandi.net for only 20 EUR for the two years. For that price you’ll get the minimum and won’t obtain a certificate with the Green Address Bar, which costs around 240 EUR / year.

When ordering the certificate, a CSR (Certificate Sign Request) will be requested. The CRS can be obtained from IIS as explained here for example, through the menu Generate Certificate Request. A few questions about who you are will be asked, the most important being the Common Name, which will be typically www.yourdomain.com  (or, better, use a wildcard, as in *.yourdomain.com). If the Common Name doesn’t match the web site domain, the user will get a warning at browsing time, so this is a sensitive step.

Installing the Certificate in IIS

Once you’ve ordered the certificate, the certificate shop will provide you with a .crt or .cer crypted content. This is the certificate. But IIS doesn’t deal with the .crt nor .cer formats, it asks for a .pfx file! This is misleading and the number one explanation on the web is this one on the Michael Richardson blog. Basically you’ll use the IIS menu Complete Certificate Request (that follows the first Generate Certificate Request). Now restart IIS or the server to make sure it’ll take care of the certificate.

Binding the Certificate to the website 443 Port in IIS

At that point the certificate is installed on the server. The certificate needs to be bound with your website port 443. First make sure that the port 443 is opened on your server, and second, use the binding IIS menu on your website. A binding entry will have to be added as shown in the picture below.

Once added just restart the website. Normally, you can now access your website through HTTPS urls. If not, you may have to tweak the DNS pointers somehow, but I cannot comment since we didn’t have a problem with that.

At that point, both HTTPS and HTTP are browsable. HTTP requests need to be redirected to HTTPS to complete the migration.

301 redirection with Web.Config and IIS UrlRewriter

HTTP to HTTPS redirection can be achieved by modifying the Web.Config file of your ASP.NET website, to tell the IIS Url rewriter how to redirect. After a few attempts based on googling, our redirection rules look like:

If you believe this can be improved, please let me know. At least it works 🙂

  • <add input=”{HTTPS}” pattern=”off” ignoreCase=”true” /> is the main redirection rule that redirects HTTP requests to HTTPS (this is called 301 redirection). You’ll find many sites on the web to test that your 301 redirection works fine.
  • Make sure to double check that urls with GET params are redirected well. On our side, url=“https://{HTTP_HOST}{REQUEST_URI}” processes GET params seamlessly
  • <add input=”{URL}” pattern=”(.*)XYZ” negate=”true” ignoreCase=”true”/> is important to avoid HTTP to HTTPS redirection for a page named XYZ. Typically, if you have special pages with POST requests, they might be broken with the HTTPS redirection, and thus the redirection needs to be discarded for those.
  • <add input=”{HTTP_HOST}” matchType=”Pattern” pattern=”^localhost(:\d+)?$” negate=”true” /> avoid the HTTPS redirection when testing on localhost.
  • <add input=”{HTTP_HOST}” pattern=”^www.*” negate=”true”/> just transforms ndepend.com requests into www.ndepend.com,
  • and  <add input=”{HTTP_HOST}” pattern=”localhost” negate=”true”/> avoids this WWW redirection on localhost.

Eliminate Mixed Content

At this point you are almost done. Yet depending on the topology of your web site(s) and resources, it is possible that some pages generate a mixed content warning. Mixed content means that some resources (like images or scripts) of an HTTPS web page are served through HTTP. When mixed content is detected, most browsers show a warning to users about a not fully secured page.

You’ll find tools to search for mixed content on your web site, but you can also crawl the site yourself and use the Chrome console to get details about mixed content found.

Update Google SiteMap and Analytics

Finally make sure that your Google sitemap now references HTTPS urls, and update your Google Analytics for HTTPS:

I hope this content saves a few headaches. I am certainly not a SSL nor an IIS expert, so once again, if some part of this tutorial can be improved, feel free to comment!

Our experience with using third-party libraries

NDepend is a tool that helps .NET developers write beautiful code. The project was started in April 2004. It is now used by more than 6 000 companies worldwide.

In more than a decade, many decisions were made, each with important consequences on the code base evolution process, sometime good consequences, sometime less good. Relentlessly dog-fooding (i.e using NDepend to analyze and improve the NDepend code base) helped us a lot to obtain more maintainable code, less bugs, and to improve the tool usability and features.

When it comes to working on and maintaining a large code base for several years, some of the most important decisions made are related to relying (or not) on some third-party libraries. Choosing whether or not to rely on a library is a double-edged sword decision that can, over time, bring a lot of value or cause a lot of friction. Ultimately users won’t make a difference between your bugs and third-party libraries bugs, their problems become your problems. Consider this:

  • Sometimes the team just needs a fraction of a library and it may be more cost-effective, and more maintainable with time, to develop your own.
  • Sometimes the licensing of a free or commercial library will prevent you from achieving your goals.
  • Sometimes the library looks bright and shiny but becomes an obsolete project a few months later and precious resources will have to be spent maintaining others code, or migrating toward a trendy new library.
  • Sometimes the library code and/or authors are so fascinating that you’ll be proud to contribute and be part of it.

Of course we all hope for the last case, and we had the chance to experience this a few times for real. Here are some libraries we’ve had great success with:

Mono.Cecil (OSS)

Mono.Cecil is an open source project developed by Jean-Baptiste Evain that can read and write data nested in .NET assemblies, including compiled IL code. NDepend has relied on Cecil for almost a decade to read IL code and other data. Both the library and the support provided are outstanding. The performance of the library is near optimal and all bugs reported were fixed in a matter of days or even hours. For our usage, the library is actually close to bug free. If only all libraries had this level of excellence…

DevExpress WinForm (Commercial)

NDepend has also relied on DevExpress WinForm for almost a decade to improve the UI look and feel. NDepend is a Visual Studio extension and DevExpress WinForm makes smooth visual integration with Visual Studio. Concretely, thanks to this library we achieved the exact same Visual Studio theming and skinning, docking controls a la Visual Studio, menus, bars and special controls like BreadCrumb to explore directories. We have never been disappointed with DevExpress WinForm. The bugs we reported were fixed quickly, it supports high DPI ratio and it is rock solid in production.

Microsoft Automatic Graph Layout MSAGL (OSS)

NDepend has relied on MSAGL for several years to draw all sorts of graphs of dependencies between code elements including Call Graphs, Class Inheritance Graphs, Coupling Graphs, Path and Cycle Graphs…  This library used to be commercial but nowadays OSS.  Here also the bugs we reported were fixed quickly, it supports high DPI ratio and it is perfectly stable in production.

NRefactory (OSS)

NDepend used to have a C# Code Query LINQ editor in 2012, a few years before Roslyn became RTM. We wanted to offer users a great editing experience with code completion and documentation tooltips on mouse-hovering. At that time NRefactory was the best choice and it proved with the years to be stable in production. Nowadays Roslyn would certainly be a better choice, but since our initial investment NRefactory still does the job well, we didn’t feel the need (yet) to move to Roslyn.


Here are a few things we prefer to keep in-house:


While there are libraries for licensing, these are vital, sensitive topics that require a lot of flexibility with time, and we preferred to avoid delegating it. This came at the cost of plenty of development/support and significant levels of acquired expertise. Even taking into account that these efforts could have been spent on product features, we still don’t regret our choice.

The licensing layer is a cornerstone in our relation with our users community and it cannot suffer from any compromise. As a side remark, several times I observed that the cost of developing a solid licensing layer postponed promising projects to become commercial for a while.


As most of application, NDepend persists and restores a lot of data, especially the large amount of data in analysis results. We could have used relational or object databases, but for a UI tool embedded in VS, the worst thing would be to slow down the UI and make the user wait. We decided only optimal performance is acceptable for our users, and optimal performance in persistence means using custom streams of bytes. The consequence of this decision is less flexibility: each time our data schema evolves, we need to put in extra effort to keep ascendant compatibility.

I underline that most of the time it is not a good idea to develop a custom persistence layer because of the amount of work and expertise required. But taken account our particular needs and goals, I think we took the right decision.

Production Logs

I explained here about our production logs system. We consider it an essential component to making NDepend a super-stable product. Here also, we could have used a third-party library. We capitalize on our own logging system because, year after year, we customized it with a plethora of production information, which was required to help fix our very own problems. We kept the system lightweight and flexible, and it still helps us improve the overall stability and correctness of our products.

Dependency Matrix and Treemap UI Components

These UI components were developed years ago and are still up to date. Both then and now, I believe there is no good third-party alternative that meets all our requirements in terms of layout and performance. A few times, we received propositions to buy those components, but we are not a component provider and don’t have plans for that.


In this post I unveiled a few core choices we made over the years. We hope this information will be useful for other teams.

A Visual Studio script that saves time and pain

After years of pain, I finally found a clean-and-definitive way to get rid of the dreadful issue Could not copy assembly, the process cannot access the file because it is used by another process!

Locked assembly

I have no idea how many .NET developers are coping with this issue, but on our side it used to be daily and there are many situations where an assembly file gets locked:

  • sometimes VS just load in-process the assembly, or the PDB file or the .xml documentation file, for an unknown reason (usually after a debug session)
  • sometimes the culprit seems to be vshost.exe
  • sometimes the culprit is the test runner process
  • sometimes, after a smoke test session, one just forgets to close all processes that hold assemblies…
  • …or sometimes it is just a zombie process that should have stopped but just didn’t!
  • and when developing a VS extension, all of those situations are happening more often

When the culprit process was not obviously identified, I started Process Explorer to kill it! And when the culprit process is my current VS instance, it means I need to restart it and interrupt current work for significant time and then lose my mental focus!!

The clean-and-definitive solution to this problem, is this script to copy in a .bat file. This script must be invoked from the VS project pre-build-events. It just moves the assembly file, the .pdb file and the .xml documentation file to a dumb location (if the .pdb or .xml file is missing no problem).

The key is that when a process locks a file, Windows authorizes to move and rename the file. I found the original idea from this stackoverflow answer, that itself found it from a Keyvan Nayyeri blog post that seems to have been removed.

To invoke this script just add this in all your VS project pre-build events command line. If you wish the script name and location to be different, just adapt $(SolutionDir)\BuildProcess\PreBuildEvents.bat.


Notice that this script does the job no matter the actual configuration (Debug or Release) and no matter if the compilation is started from VS or from any other script.


NDepend updated to Version 6.2

NDepend version 6.2 has just been released. We have addressed over 20 bug fixes, including a blocker one for Visual Studio 2015 update 1 Git Controls.

More specifically the new Visual Studio 2015 Update 1 Git controls in the Visual Studio status bar were interacting with the NDepend Visual Studio extension status bar control. As a consequence this was provoking VS UI freezing. That is fortunate that the Visual Studio team warned partners (VSIP) a few weeks ago that they were adding controls to the status bar. The issue was coming from a synchronous usage of the WPF dispatcher to implement the NDepend progress & status circle. Invoking the dispatcher asynchronously fixed the issue.


We also stumbled on an unusual issue due to an unfixed Windows bug. When working with DataGridView with many rows (like 1000+) we can face an unmanaged StackOverflowException that crashes the process. The Windows bug is explained here http://stackoverflow.com/a/14716720/27194 and as far as we know it is not fixed. The problem occurs only when the Windows process TabTip.exe runs (“Touch Keyboard and Handwriting Panel Service“) and the stackoverflow link explains that the only way to prevent it is to disable this touch keyboard service. We’re going the hard way and actually when NDepend starts, it now tries to kill this process. Most of the time it’ll work, even if the Windows user is not administrator. If you get any inconvenience with this rough fix, please let us know.

Apart these two fixes, many other bugs were fixed and some improvements were added (see the complete list here). Bugs fixed also includes some incorrect results that were happening because the way Roslyn emits IL has significantly changed in some situations, and NDepend relies a lot on IL code analysis.




NDepend Case Study: Increasing Development Efficiency in the Medical Laboratory Sector

Developing applications for use in the health care industry is stressful because the margin of error is almost non-existent. Whether your tool is for treatment, research, or analysis, it needs to be dependable and accurate. The more complex the application is, the higher the chance for errors and delays in development. Dependable companies abide by rigorous methodologies to develop their code before deploying it to clients. In this NDepend case study, we learn why a company in this sector chose NDepend, and why it became an integral part of their development process.

Stago works in the medical lab industry, producing lab analysis tools that focus on haemostasis and coagulation. Working hard for over 60 years and valuing long term investments, they have created a name for themselves in the industry. A few years ago, they wanted to make their software development process more efficient. In addition, they wanted to easily enforce their own best practices and code quality standards across their teams. The goal was to be able to catch issues earlier in the development cycle to cut costs and time spent on quality assurance post-development.

“We selected NDepend after reviewing all the other options on the market and it quickly became the backbone of our development effort.”
– Fabien Prestavoine, Software Architect at Stago

We are very grateful for Stago for sharing their success story with us. Stories such as these is one of the main driving forces behind creating one of the most comprehensive and powerful .NET analysis tool on the market. Since implementing NDepend, Stago has:

  • Easily met all delivery deadlines
  • Cut both cost and time spent on quality assurance
  • Delivered a consistently dependable product
  • Improved communication between their developers and architects

To read more about how NDepend helped Stago streamline their development process, click here to download a PDF of the complete case study.

Or check out this slideshow: