I have several Unmanaged C++ written lib files which I need to link to Managed C++ dll.
Then I need to invoke functions of this Managed C++ from C# application.
First step is OK - Managed C++ dll is created, I can see with ildasm that it exports functions I need. However when I try to call this function from my C#-written test app it says:
An unhandled exception of type 'System.IO.FileLoadException' occurred in Unknown Module.
A procedure imported by {MyManagedCPP.dll} could not be loaded.
This message goes from VS2010.
I made simple experiment - removed dependencies from all lib files in Managed C++ dll and rebuild it.
With this change it is OK - app starts, I can call functions of Managed C++ dll from C# test app.
Is it not possible by design to call managed c++ functions when dll has static linkage with lib files? Technical restriction? Or there is some workaround?
Thanks
You no doubt have an implicit dependency on a native DLL. It isn't clear from the question what DLL that might be. It could be msvcrxx.dll for example, a runtime support library for native C++ code. Which would be rather bad, you don't want to mix CRT versions. Such a missing DLL otherwise prevents the C++/CLI assembly from getting loaded, producing the FileLoadException.
If you have no idea what that DLL might be then you could use SysInternals' ProcMon utility. The trace will show you the program searching for the DLL and not finding it. If it is msvcrxx.dll then be sure to rebuild the .lib files using the same compiler version you used to build the C++/CLI assembly. If it is something else then make sure you copy that DLL to the build directory.
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I have a c++ project compiled with /clr support(e.g. wrapper.dll). This project(wrapper.dll) is a wrapper between .Net enviroment and unmaged dll(e.g. noCode.dll), which inherits from. I dont have access to code of inherited dll(noCode.dll), but I can link it to my wraper (by noCode.lib and noCode.h files).
When I want to use my wraper(wrapper.dll) in c# project I reference it and have to copy my unmanaged dll(noCode.dll) to location of c# project execution.
Is it possible to merge c++ unmamaged dll(noCode.dll) to managed dll(wrapper.dll) to allow to use only one file by reference(noCodeWrapper.dll) in c# projects?
It is not possible to link DLL files together.
But you can add that nocode.LIB to your DLL and then you don't need [DllImport]. Since you have LIB and H files, you can call the "nocode" functions directly from your managed C++ code.
If you had access to noCode.dll source code you could integrate it with wrapper.dll. Otherwise merging DLL binaries is not a task that could give predictable results.
I'm working on a C# component which consists of two DLLs:
A .DLL written in C++/CLI exporting a symbol; unfortunately, this DLL dynamically links against the CRT and there doesn't seem to be a way around that.
A C# assembly.
The C++/CLI DLL gets loaded and then loads the C# assembly (and forwards most calls to it). Is it possibly to simplify this scenario so that I export a symbol from the C# assembly right away?
You can export your functionallity from C# as a COM server this way it should be pretty easy to call it from C++ as you would do with any other non-C# COM object.
I ended up going for the solution described in http://www.codeproject.com/Articles/37675/Simple-Method-of-DLL-Export-without-C-CLI
The general approach is to have a dedicated attribute which is used to decorate the functions to be exported. After building the assembly, ildasm is used to disassemble it. The resulting IL is patch a little bit so that the previsouly decorated functions are exported, then the IL is assembled into an assembly again.
My project structure is as follow:
ASP.NET calling C# layer calling Managed C++ calling Native C++
(i'm trying to avoid using interop so this is why the managed c++ layer)
I wrote unit test that test the C# layer and it works fine.
When I try to run the asp.net page i'm getting: "Could not load file or assembly..." error.
I figured out that when i copy paste the Native C++ dll to "Temporary ASP.NET Files" (to the corresponding folder) the site works.
It seems that the Managed C++ code can find the Native C++ code only if it resides in the same folder - obviously I can't have my Native dll in the temp files.
Is there a way to set the Native in a global place(doesn't work with System32)?
Thanks for you comments.
It boils down to one option:
It is security issue
i set up the server it self with the code and it runs under the cassini, but when i publish it(to run under iis7) i'm getting "Could not load file or assembly ...."
i'm running IIS7 with ApplicationPoolIdentity , .net 4 Integrated
Thanks a lot,
Pini.
Well technically using Managed C++ in this way is a form of Interop between native / managed code, the commonly used alternatives being COM and P/Invoke. This is purely a terminology thing however, you would get the same issue using P/Invoke.
This blog article Loading C++ Assemblies in ASP.Net might help you out - In short you need to either:
Set the %PATH% environment variable before the Managed C++ assembly attempts to load your native C++ dll.
Use the DllImport attribute to set the dll path (not applicable in your case as you aren't using P/Invoke)
Manually load the C++ dll yourself (e.g. with LoadLibrary) before the Managed C++ assembly attempts to load your native C++ dll.
I suspect that installing your dll to Win SxS would also work, but I don't know enough about how this works to be sure.
You can set your path variable?
You set it by going to the Properties of "My computer"/"Computer (Windows-PauseBreak) and then clicking advanced settings. Click advanced. Environment variables. Modify "Path" under system variables as needed.
I had to flip a bool in the ApplicationPoolIdentity. One of the filed in the properties says "enable 32bit" and that did the trick :) the default is False
My server is 64bit and i build my native with 32bit.
I am wondering how I would go about correctly setting up a C++/CLI library that wraps native c++ code that has several dependencies. I have tried both statically and dynamically linking the native library to its dependent libraries with no luck.
The Managed C++/CLI dll builds just fine and can be added as a reference to a C# project. However when I attempt to use any of the defined classes i receive either a BadImageFormatException or FileNotFoundException depending how i linked. I believe I need to specify the dependent libraries in the CLI library so it is loaded in the manifest but I am unsure of the process. Also because i know it will come up, I have verified that all of the libraries involved are built on the x86 architecture.
I figured out the problem and everything is working correctly now. It was a combination of several incorrect things all happening together.
If anyone has the same issue, I resolved it by setting up the following:
1) The Boost libraries that were referenced (specifically boost_thread) needed to be compiled with BOOST_THREAD_USE_DLL preprocessor (other boost libraries may need BOOST_ALL_DYN_LINK to just dynamically link everything). This is apparently a common issue.
2) I verified that all dependencies were in system Path (like R Ubben reiterated)
3) I used the DependencyWalker (depends.exe from sourceforge) to analyze my compiled managed DLL. It turned out that the libpq.lib library being used actually referenced additional DLLs that were not included in the lib folder but in the bin folder. So that need to be added to the Path.
4) Part of my wrapper was using the #include header for lists. This forced my library to link against 2.0 framework dependent libraries. This was not compatible with my 4.0 client targeted C# application. This was only made known by parsing through the Warnings from compiling (previously hidden due to C++ generating too many..foolish i know). However this was resulting in a System.BadImageFormateException being thrown despite everything targeting the same x86 architecture.
Hope that helps anyone else who has the same problem. The BadImageFormateException and FileNotFoundException were entirly too vague and unhelpful.
You should make the C++ dll in release mode and use extern "C" for public static things.
I have gotten that error when the dependent libraries were not in the path. The wrapper library is found because of the reference, but the reference does not also take care of the dependent libraries. Try placing them explicitly where the program is executing.
I'm trying to use the lame_enc.dll file from LAME in a C# project, but adding the thing seems impossible.
I keep getting an error that says that a reference could not be added and to please check if the is accessible, a valid assembly or COM component.
I have no C++ experience, though I would like to use the functionality. Right now I'm using Process from the .NET framework to call lame.exe and do stuff, but I'd like to know if there's another way.
You can only add managed assemblies as a reference to a managed project. What I normally do in this situation is to add it as ressource instead with "copy local" settings. That way the DLL is tied to and deployed with your project. I then use DllImport to manually get the APIs I need from that DLL.
You have to use P/Invoke to call unmanaged APIs from managed code.
To use an unmanaged dll (native C++) in C#, you have to use DllImport, not adding a reference to the project in visual studio (and that is why you get an error).
Here is the documentation of DllImport from the MSDN.
You will need to use PInvoke to call functions in your native lame dll. However, you will only be able to call functions that have been exported as "C" style.
You can use a tool like "PInvoke Interop Assistant" that will help you when working out the PInvoke call signatures to make calls from C# to your native dll:
http://clrinterop.codeplex.com/releases/view/14120