I might be a bit stupid, but I want to create a tool in Visual Studio in C# and want to call third party tools via their API-DLLs. The only topics I found here are dealing with one of the two methods that I already know:
Compilation time: add a reference to "C:\FooTool\foo.dll" in my project + "using fooToolNamespace.fooToolClass" in my code (compilation time) --> I can "naturally" use the classes of the DLL and will even get full IntelliSense support if a suiting XML-file is available with the DLL. Also compilation time checks will be done for my usage of the dll.
Dynamic (run time): calling e.g. Assembly.LoadFile(#"C:\FooTool\foo.dll") and then using reflection on it to find functions, fields and so on --> no IntelliSense, no compilation time checks
So I actually have the DLL at hand and thus option 1) would be nice during development. But if my tool is used on a different PC, the third-party DLL might be in a different path there, e.g. "C:\foo\foo.dll" and "C:\bar\foo.dll".
In my understanding using a copy of "foo.dll" will not work, because "foo.dll" might have dependencies, e.g. requiring other files of the FooTool-directory. Thus in my understanding I have to call the DLL which is "installed" to the target PC and not a local copy of it.
So can I somehow change the path where my tool accesses the "foo.dll" at runtime and still use method 1) during development?
Or is there another way of doing things?
Or am I just dumb and there is a simple solution for all this?
Thanks a lot for the help and have a great day
Janis
To be able to use option 1 (a referenced DLL), you need to put the DLL somewhere "where your EXE (or, more precisely, the Assembly Resolver) can find it" on the customer's PC.
So where does the assembly resolver look for your DLL?
In the directory where the EXE resides (for desktop/console applications) or the bin subdirectory (for web applications). Since you mention that your DLL requires other dependencies as well, you'd need to copy them to that location as well.
The Global Assembly Cache (GAC). If your dependency supports this, installing it to the GAC ensures that it can be found by your application.
These two are the "supported" scenarios. There is also the possibility to tweak the assembly resolver to look into other directories as well, but that should be reserved for special cases where the other two options failed. (We had such a case and solved it with a custom AssemblyResolve handler on the application domain.)
I got a DLL registered in the GAC which has a bug in it (v4.2.0).
I've therefore fixed that bug, updated the file version only (v4.2.1) (keeping the assembly version, v4.2.0) and built a new MSI package.
The problem is that the DLL is not installed in the GAC. I verified this by right-clicking on the DLL in C:\Windows\Microsoft.NET\assembly\GAC_MSIL\MyDLL\v4.0_4.2.0.0__2269313d92725976 and checked the file version, which is still v4.2.0 There are also no other folders created under C:\Windows\Microsoft.NET\assembly\GAC_MSIL\MyDLL.
But! If I uninstall the first version and then install the new DLL it get's installed OK in the GAC.
Am I approaching this the wrong way? Our applications are set to use specific versions, so just creating assembly version v4.3.0 and install it in the GAC wont work.
Update
I've found the article about publisher policies ( http://support.microsoft.com/kb/891030) and are attempting that instead. I've generated the policy assembly. But Visual Studio crashes when I try to add it to the setup project =(
I've also tried to add it as a content file to the primary project (and then add content files to GAC). But then it complains on the assembly not being signed.
So I'm still stuck.
Updating the [AssemblyFileVersion] for a bug fix is usually the right approach, although it gets iffy if you do so for an assembly in the GAC. You run the risk of breaking another app that also uses the assembly and unintentionally depends on the buggy behavior to function correctly. An unintentional mistake like renaming a public method is of course always a good way to break an app, the road to DLL Hell is paved with many good intentions that turned out bad.
The GAC however only pays attention to [AssemblyVersion] and ignores the file version. To get the updated assembly to replace the existing one you do have to remove the old one first. This is intentional, preventing accidental replacement.
A <bindingRedirect> in the .config file of the app you want to repair will be a lot easier to get going than a publisher policy.
I believe this has to do with what parameters of a .NET assembly the GAC uses to give it a unique identifier. If the assembly version is one of those uniqueness parameters, but file version is not, that may explain your symptoms. Specifically this pertains to the GACs need for a strong named assembly
This link says as much
http://msdn.microsoft.com/en-us/library/wd40t7ad.aspx
I have .net dll, it use different .net dll with PublicToken set to null. Now I have to use the same version of different dll but with PublicToken set to some other value. Is there a way to use it without a need of recompilation of first dll (I do not have sources).
I don't think there is a clean way of doing this, mainly because what you are trying to do is defeat the very purpose of the Strong Naming concept. bindingRedirect only works on version, not the key. The only way that I can think of is to disable Strong Name Verification:
sn.exe -Vr TheAssembly
You can learn more about that here.
The problem with it is, it has to be done on every machine this is run.
Another alternative is to use a tool like Mono.Cecil to strip the Public Key Token from the Module's Assembly References so it no longer cares. If it is strong named itself, you'd have to remove that too. This option generally works, but will in most cases violate any form of EULA the assembly comes with if it is a commercial product.
Let's assume I have two assemblies:
MyExecutable.dll version 1.0.0
MyClassLibrary.dll version 1.0.0
Now, MyExecutable.dll currently uses MyClassLibrary.dll's classes and methods (which include some algorithms). Most of those algorithms were made on the run, being that later I'll want to refine them if needed. This means, I won't change the interface of those classes but the code itself will see some changes.
The question at hand is, MyExecutable.dll will be expecting MyClassLibrary.dll 1.0.0 and I'll want it to use version 1.0.1 (or something like that). I don't want to have to recompile MyExecutable.dll(because actually there might be more than just one executable using MyClassLibrary.dll). Is there a solution for this problem? I've heard about the GAC, but if possible I'd like to stay away from it.
Thanks
You are looking for Assembly Binding Redirection - this is a configurable way to tell .NET what version assemblies to use.
The first solution is Assembly Binding redirection, already recommended by Oded.
It is advantageous if you have a smaller .dll and want to make something work with its newer versions.
The second option is creating a separate assembly for the interfaces, and referencing only that from the executable.
This way, you can allow third parties to build stuff against your library without giving them the exact library's assembly. (Eg. they can't decompile it with Reflector, so it is more secure this way.)
As long as the interface assembly doesn't change, you can change other stuff in the library pretty much as you want.
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