I am having an issue (i.e. ReflectionTypeLoadExceptions) with assembly loading in a netcore3.1 application, specifically when using "NUnit.ConsoleRunner.NetCore --version 3.12-beta2" to load unit test assemblies which depend on other assemblies, CopyLocal is set to false for the project-references, although all assemblies are in the same directory.
When CopyLocal is set to false for a particular reference, the .deps.json file will not contain all the entries required for the dependee to be loaded by the AssemblyLoadContext directly, and so the AssemblyLoadContext.Resolving callback/event is fired, but not handled in nunit, or handled incorrectly. The ReflectionTypeLoadException is thrown later, when nunit calls assembly.GetTypes().
A simple demo of the issue can be found here: https://github.com/Ian144/NunitAssemblyLoadIssue.git, that includes a console-app that uses a custom AssemblyLoadContext to demonstrate the issue, or if "NUnit.ConsoleRunner.NetCore --version 3.12-beta2" is installed, just run "nunit AssemblyA.dll" from the output directory. In the demo, AssemblyA contains nunit tests, and has a project reference to AssemblyB with copyLocal set to false.
So, is there an issue with the nunit netcore runner, which should be handling the AssemblyLoadContext.Resolving event? or is there a different way to get assembly loading working under this circumstance?
thanks, Ian
There's some known issues with assembly loading in the beta2 version that were highlighted in the release notes.
The good news is, we've just merged a pull request that we think might fix it. There's a link to the pull request below, which also has details of where to find an updated version, and an appeal for people to try it out. Would appreciate if you could give it a whirl and let us know how it goes! 👍
https://github.com/nunit/nunit-console/pull/942
I have a solution with 3 projects. I made it as a test:
1) The WinFormsProject (setted as Main project): It is just a form that throws an exception when clicking a button. Before throwing the exception, it makes some assignations with an object of the class Person (who is in another assembly).
2) The ConsoleProject: It's another assembly with the same idea: it only plays a little with an object of the class Person and then throws an Exception.
3) The AspectTest: it's an assembly which has defined the class Person and an aspect (called LogBoundary) (inherited from OnMethodBoundaryAspect) who logs OnEntry(), OnExit(), OnSuccess() and OnException().
The three assemblies are configured through an "AspectInfo.cs" class to target every method but the "CompileGenerated" ones. So:
[assembly: LogBoundary()]
[assembly: LogBoundary(
AttributeExclude = true,
AttributePriority = 0,
AttributeTargetMemberAttributes = MulticastAttributes.CompilerGenerated)]
The problem is that all methods in the assembly AspectTest are being logged, but the ones in WinFormsProject not. I have no idea why.
Some things to consider:
Every assembly has a reference to postsharp. So every aspect is
being correctly recognized by the compiler.
If I set the ConsoleProject as the Main project, it works
correctly. The problems comes only with WinFormsProject.
WinFormsProject references AspectTests (of course!).
ConsoleProject references AspectTests (of course!).
There is no dependency between WinFormsProject and
ConsoleProject.
Any help would be great, and if you still need some info about this, please ask me (I might forget to tell something).
Thanks!
To introduce the aspects into your code, PostSharp needs to execute during build time after the main compilation step. This means that adding a reference to PostSharp.dll in your project is not enough - the build sequence of the project needs to be modified as well.
PostSharp automatically integrates into the build process when you install the NuGet package. If PostSharp doesn't run during build, then you can try to reinstall the package.
Well, I am a bit ashamed of the reason, but it might pass to anyone, so here's the problem and how I solved it.
The problem was: as I added the postsharp.dll as a reference manually and not with NuGet (because I had no internet on that moment) the references were ok, all compiled as expected, but as said, aspects didn't worked on the Winforms project. Maybe I missed to do something else.
The solution, therefore was so easy as to add postsharp through Nuget. Just that.
Now everything works. If someone has a better idea of the description of the problem, it would be good to know it.
thanks, AlexD.
My question is relevant to this question, but I've somehow moved a step further and implemented a test framework using nunit.
When I run the test framework addin inside Revit, the testing framework somehow locks the test assemblies making it impossible to recompile the test assemblies. To get around it, I tried making a shadow copy so the nunit test runner runs on the copied assemblies. But once I run the tests for the first time, the subsequent test runs does not work on updated copies. It is like the test runner caches the dlls and always tries to run tests on cached copy.
So each time the test assembly is updated, I need to close-reopen Revit to run the tests which is a real pain. The main reason I implemented the testing framework for Revit was to be able to do BDD/TDD using Revit API.
This is a code snippet of how I run the tests:
TestPackage theTestPackage = new TestPackage(testDll);
RemoteTestRunner testRunner = new RemoteTestRunner();
testRunner.Load(theTestPackage);
TestResult testResult = testRunner.Run(new NullListener());
Does anyone have any idea how to solve this?
You can try loading the assemby for testing with the Assembly.Load(byte[]) method. I'm not sure if your test runner can handle this, but this will give you an assembly to work on that is loaded from a byte stream in memory. Therefore the original assembly file can be recompiled anytime and you can have as many concurrent versions of this assembly loaded as you like. They are all separate, with separate types.
I use a similar strategy with the RevitPythonShell script loadplugin.py for loading plugins at runtime and then exercising them for testing. This seems to work quite well except for WPF controls defined in XAML. I suspect the XAML parser and loader keeps a cache of the types, but haven't been able to look into this yet due to time constraints.
So here's the problem. I'm writing some StyleCop plug-in assemblies for use at the company I work for. As such, these assemblies need to reference Microsoft.StyleCop.CSharp.dll for example, which is strongly named.
The problem comes in that if I build this and pass it along to the developers in my group, they must have the same version of the StyleCop dll (currently 4.3.3.0) or it fails to load.
What is the best way to make my add-on rules DLL more independent? Should I just install my 4.3.3.0 version of those subordinate StyleCop dlls in the GAC? Can an assembly (vs an application) use a policy file?
Oh, and one of the main problems is i would like it to work with ANY version of StyleCop the client has installed (or at least 4.3.3.0 or later) if possible.
Many thanks in advance.
Yes you should just install the same version for the other developers. If you do not, you may have unpredictable runtime failures due to changes within StyleCop. Presumably that is why they bothered to increment the version number.
If you don't want to do this, you can configure a different assembly binding in the app.config file. In the config the actual version number which you intend to use at runtime is needed. And yes, this can even be done via policy. But again, I think you are better served by including the correct DLL in the first place.
In your project, go to the properties on the StyleCop reference. Try setting the "Specific Version" property to false.
To preface, I've been working with C# for a few months, but I'm completely unfamiliar with concepts like deployment and assemblies, etc. My questions are many and varied, although I'm furiously Googling and reading about them to no avail (I currently have Pro C# 2008 and the .NET 3.5 Platform in front of me).
We have this process and it's composed of three components: an engine, a filter, and logic for the process. We love this process so much we want it reused in other projects. So now I'm starting to explore the space beyond one solution, one project.
Does this sound correct? One huge Solution:
Process A, exe
Process B, exe
Process C, exe
Filter, dll
Engine, dll
The engine is shared code for all of the processes, so I'm assuming that can be a shared assembly? If a shared assembly is in the same solution as a project that consumes it, how does it get consumed if it's supposed to be in the GAC? I've read something about a post build event. Does that mean the engine.dll has to be reployed on every build?
Also, the principle reason we separated the filter from the process (only one process uses it) is so that we can deploy the filter independently from the process so that the process executable doesn't need to be updated. Regardless of if that's best practice, let's just roll with it. Is this possible? I've read that assemblies link to specific versions of other assemblies, so if I update the DLL only, it's actually considered tampering. How can I update the DLL without changing the EXE? Is that what a publisher policy is for?
By the way, is any of this stuff Google-able or Amazon-able? What should I look for? I see lots of books about C# and .NET, but none about deployment or building or testing or things not related to the language itself.
I agree with Aequitarum's analysis. Just a couple additional points:
The engine is shared code for all of the processes, so I'm assuming that can be a shared assembly?
That seems reasonable.
If a shared assembly is in the same solution as a project that consumes it, how does it get consumed if it's supposed to be in the GAC?
Magic.
OK, its not magic. Let's suppose that in your solution your process project has a reference to the engine project. When you build the solution, you'll produce a project assembly that has a reference to the engine assembly. Visual Studio then copies the various files to the right directories. When you execute the process assembly, the runtime loader knows to look in the current directory for the engine assembly. If it cannot find it there, it looks in the global assembly cache. (This is a highly simplified view of loading policy; the real policy is considerably more complex than that.)
Stuff in the GAC should be truly global code; code that you reasonably expect large numbers of disparate projects to use.
Does that mean the engine.dll has to be reployed on every build?
I'm not sure what you mean by "redeployed". Like I said, if you have a project-to-project reference, the build system will automatically copy the files around to the right places.
the principle reason we separated the filter from the process (only one process uses it) is so that we can deploy the filter independently from the process so that the process executable doesn't need to be updated
I question whether that's actually valuable. Scenario one: no filter assembly, all filter code is in project.exe. You wish to update the filter code; you update project.exe. Scenario two: filter.dll, project.exe. You wish to update the filter code; you update filter.dll. How is scenario two cheaper or easier than scenario one? In both scenarios you're updating a file; why does it matter what the name of the file is?
However, perhaps it really is cheaper and easier for your particular scenario. The key thing to understand about assemblies is assemblies are the smallest unit of independently versionable and redistributable code. If you have two things and it makes sense to version and ship them independently of each other, then they should be in different assemblies; if it does not make sense to do that, then they should be in the same assembly.
I've read that assemblies link to specific versions of other assemblies, so if I update the DLL only, it's actually considered tampering. How can I update the DLL without changing the EXE? Is that what a publisher policy is for?
An assembly may be given a "strong name". When you name your assembly Foo.DLL, and you write Bar.EXE to say "Bar.EXE depends on Foo.DLL", then the runtime will load anything that happens to be named Foo.DLL; file names are not strong. If an evil hacker gets their own version of Foo.DLL onto the client machine, the loader will load it. A strong name lets Bar.EXE say "Bar.exe version 1.2 written by Bar Corporation depends on Foo.DLL version 1.4 written by Foo Corporation", and all the verifications are done against the cryptographically strong keys associated with Foo Corp and Bar Corp.
So yes, an assembly may be configured to bind only against a specific version from a specific company, to prevent tampering. What you can do to update an assembly to use a newer version is create a little XML file that tells the loader "you know how I said I wanted Foo.DLL v1.4? Well, actually if 1.5 is available, its OK to use that too."
What should I look for? I see lots of books about C# and .NET, but none about deployment or building or testing or things not related to the language itself.
Deployment is frequently neglected in books, I agree.
I would start by searching for "ClickOnce" if you're interested in deployment of managed Windows applications.
Projects can reference assemblies or projects.
When you reference another assembly/project, you are allowed to use all the public classes/enums/structs etc in the referenced assembly.
You do not need to have all of them in one solution. You can have three solutions, one for each Process, and all three solutions can load Engine and Filter.
Also, you could have Process B and Process C reference the compiled assemblies (the .dll's) of the Engine and Filter and have similar effect.
As long as you don't set the property in the reference to an assembly to require a specific version, you can freely update DLLs without much concern, providing the only code changes were to the DLL.
Also, the principle reason we
separated the filter from the process
(only one process uses it) is so that
we can deploy the filter independently
from the process so that the process
executable doesn't need to be updated.
Regardless of if that's best practice,
let's just roll with it. Is this
possible?
I actually prefer this method of updating. Less overhead to update only files that changed rather than everything everytime.
As for using the GAC, whole other level of complexity I won't get into.
Tamper proofing your assemblies can be done by signing them, which is required to use the GAC in the first place, but you should still be fine so long as a specific version is not required.
My recommendation is to read a book about the .NET framework. This will really help you understand the CLR and what you're doing.
Applied Microsoft .NET Framework Programming was a book I really enjoyed reading.
You mention the engine is shared code, which is why you put it in a separate project under your solution. There's nothing wrong with doing it this way, and it's not necessary to add this DLL to the GAC. During your development phase, you can just add a reference to your engine project, and you'll be able to call the code from that assembly. When you want to deploy this application, you can either deploy the engine DLL with it, or you can add the engine DLL to the GAC (which is another ball of wax in and of itself). I tend to lean against GAC deployments unless it's truly necessary. One of the best features of .NET is the ability to deploy everything you need to run your application in one folder without having to copy stuff to system folders (i.e. the GAC).
If you want to achieve something like dynamically loading DLL's and calling member methods from your processor without caring about specific version, you can go a couple of routes. The easiest route is to just set the Specific Version property to False when you add the reference. This will give you the liberty of changing the DLL later, and as long as you don't mess with method signatures, it shouldn't be a problem. The second option is the MEF (which uses Reflection and will be part of the framework in .NET 4.0). The idea with the MEF is that you can scan a "plugins" style folder for DLL's that implement specific functionality and then call them dynamically. This gives you some additional flexibility in that you can add new assemblies later without the need to modify your references.
Another thing to note is that there are Setup and Deployment project templates built into Visual Studio that you can use to generate MSI packages for deploying your projects. MSDN has lots of documentation related to this subject that you can check out, here:
http://msdn.microsoft.com/en-us/library/ybshs20f%28VS.80%29.aspx
Do not use the GAC on your build machine, it is a deployment detail. Visual Studio automatically copies the DLL into build directory of your application when you reference the DLL. That ensures that you'll run and debug with the expected version of the DLL.
When you deploy, you've got a choice. You can ship the DLL along with the application that uses it, stored in the EXE installation folder. Nothing special is needed, the CLR can always find the DLL and you don't have to worry about strong names or versions. A bug fix update is deployed simply by copying the new DLL into the EXE folder.
When you have several installed apps with a dependency on the DLL then deploying bug fix updates can start to get awkward. Since you have to copy to the DLL repeatedly, once for each app. And you can get into trouble when you update some apps but not others. Especially so when there's a breaking change in the DLL interface that requires the app to be recompiled. That's DLL Hell knocking, the GAC can solve that.
We found some guidance on this issue at MSDN. We started with two separate solution with no shared code, and then abstracted the commonalities to a shared assemblies. We struggled with ways to isolate changes in the shared code to impact only the projects that were ready for it. We were terrible at Open/Close.
We tried
branching the shared code for each project that used it and including it in the solution
copying the shared assembly from the shared solution when we made changes
coding pre-build events to build the shared code solution and copy the assembly
Everything was a real pain. We ended up using one large solution with all the projects in it. We branch each project as we want to stage features closer to production. This branches the shared code as well. It's simplified things a lot and we get a better idea of what tests fail across all projects, as the common code changes.
As far as deployment, our build scripts are setup to build the code and copy only the files that have changed, including the assemblies, to our environments.
By default, you have a hardcoded version number in your project (1.0.0.0). As long as you don't change it, you can use all Filter builds with the Process assembly (it only knows it should use the 1.0.0.0 version). This is not the best solution, however, because how do you distinguish between various builds yourself?
Another option is use different versions of the Filter by the same Process. You should add an app.config file to the Process project, and include a bindingRedirect element (see the docs). Whenever the Runtime looks for a particular version of the Filter, it's "redirected" to a version indicated in the config. Unfortunately, this means that although you don't have to update the Process assembly, you'll have to update the config file with the new version.
Whenever you encounter versioning problems, you can use Fuslogvw.exe (fusion log viewer) to troubleshoot these.
Have fun!
ulu