I have a C source code written in VC++6.0 and I need that code to be used in a C# application which I am coding.
I have done few things to make that happen, I have run that C source file in release mode and have generated the intermediate.manifest file and the other files there, can I use any of these file to make my problem solved.
What you want to do is import the dll like this:
[DllImport("user32.dll")]//This is where you identify your dll...
public static extern int MessageBoxA( //This would be an object from your dll
int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, "Hello World!", "My Message Box", 0);
}
The keywords that you need to search on to learn about this are "running unmanaged code" and "PInvoke".
Another alternative is to wrap the C code in managed C++. Microsoft calls it C++/CLI. Anyways, you then compile an 'assembly' from that wrapper. An assembly is just a DLL that contains managed code. Then you can 'reference' (the managed equivalent of linking) that 'wrapper' from a fully managed C# application.
So the dependency could look like this:
C -> Managed C++ -> C#
If you are comfortable enough wrapping up c code in c++ you could easily make a dll by following this microsoft guide. It details how to go about creating a dll in C++. If you need a more in-depth explanation though feel free to get back to me, and I will try and knock up a quick how-to.
Also let me know if you use a different IDE or environment and I can taylor the answer to suit your needs more precisely.
Might be later on today though as am pressed for time at the moment.
Related
I have written a selenium script in C# and now I want to expose all functions and use them all in c++ code. My point is to deliver a dll to sb who wants to use this dll in pascal (delphi). The C# code is a complete code and all I want to do is to make a bridge between my C# and pascal.
I found out that pascal is an unmanaged language so C# code, which is a managed one, can not be consumed in pascal. For that reason, I started to write a c++ dll that uses my C# dll and makes a bridge between my C# and pascal code.
I've read all available topics on stackoverflow and these are what I've found useful:
expose my functions using COM
using c++/cli to communicate with my C# dll.
I started with the first one. I was able to create COM visible dll and use that in my c++ native code but I had problems with data types. I found it hard and moved on to the second option. But I'm not sure if I can wrap all my functions like that and let unmanaged languages use them.
a sample of my c# code:
namespace MainEngine
{
public static class StartMainEngine
{
public static void test_pascal(out string _result)
{
_result = "Hello World!";
}
}
}
my c++/cli code(I have referenced to my dll and visual studio shows me all functions inside my dll. So, It's not a dll import issue):
#using<ManagedLibrary.dll>
using namespace MainEngine;
char* r;
StartMainEngine::test_pascal(r);
Please guide me through this and let me know if I'm doing this in the correct way to be able to consume this dll in pascal.
It's possible using COM, CLR or IPC
Full answer you can find in this topic here
I am working on creating a C++/CLI wrapper so that I can access a C# library in native C++. I've got about 60% of the wrapper finished, but I'm hitting a snag. The SDK for the C# library gives the method inputs/outputs as:
public bool GetNumBytesReceived(ref ulong numBytesReceived)
I'm at a loss as to how to grab numBytesReceived and pass it on to native C++. I feel like this question must have been asked before on SO, but I'm only seeing things that try to go the other way (from native C++ to C#). I've gotten the following to compile for my C++/CLI wrapper, but it gives a NullReferenceException when I access it from native C++:
public: bool NumBytesReceived(unsigned long long& numBytesReceived) {
return _CSManagedClass->GetNumBytesReceived(numBytesReceived);
}
I've also also been able to get it to compile without the input reference (&). Based on my debugging, the issue appears to be in the C++/CLI wrapper, I just don't know where.
Any help is appreciated, and I apologize if this has been asked already. I am still relatively green in the C family of languages.
I'm trying to use the SPARK particle system in OpenTK.
my project contains the header files in folders, with just two header files which only includes the others, and the folders contain the source files too.
I have tried several approaches so far, but nothing has worked for me yet, those are what I've tried:
1. P/Invoke
This is writing some code in your C++ project which built the dll and then using the DllImport attribute in C# (which obviously needs using System.Runtime.InteropServices;). I discovered the hard way that this doesn't work with classes, it only works for methods outside classes, so this approach was ineffective.
2. Wrapper classes
This is writing a class that contains a pointer to the original class. I discovered that the difficulty actually arises from calling unmanaged code(no automatic memory management) from managed code, that's why wrapper classes are needed, and that's why you have to redefine methods' signatures and let them call the original methods.
Of course this has advantages, like naming the classes and methods in a better way, but the library is so big so you can see the effort of this.
3. Use of an automatic wrapper:
This is a good approach, especially with xInterop++. I was really optimistic about this and thought it would work, it says "give me the .h files and the dll and I'll build the .NET dll for you". Good but doing so gives an error; in brief:
You must make sure .h files and the dll are consistent and that the
library works in a C++ project.
I have tried several things to deal with this error:
Knowing what the dll contains: it is difficult as I learned from Googling and from this site, so my try failed.
Putting header files in a new project and building it: received errors, fixed them, and then built the project and it worked well. I uploaded the dll file with the header files to xInterop. It then told the classes that were found but would then state that nothing was found! I searched and learned that the compiler must be told which classes are needed to be exposed by the dll by marking every class that is needed using the following statement:_declspec(dllexport).
I used Find & Replace to fix this thing and tried again and classes were shown, so I launched xInterop and received the same error.
It asked to ensure that the dll works. After verifying that the file worked I launched the program and linker errors were produced.
Here is where I'm stuck, these are the linker errors I get:
main.obj : error LNK2019: unresolved external symbol "void __cdecl
SPK::swapParticles(class SPK::Particle &,class SPK::Particle &)"
(?swapParticles#SPK##YAXAAVParticle#1#0#Z) referenced in function
"private: void __thiscall SPK::Pool::swapElements(class SPK::Particle &,class SPK::Particle
&)" (?swapElements#?$Pool#VParticle#SPK###SPK##AAEXAAVParticle#2#0#Z)
main.obj : error LNK2001: unresolved external symbol "unsigned int
SPK::randomSeed" (?randomSeed#SPK##3IA) main.obj : error LNK2001:
unresolved external symbol "unsigned long const SPK::NO_ID"
(?NO_ID#SPK##3KB) main.obj : error LNK2001: unresolved external symbol
"public: static float const * const SPK::Transformable::IDENTITY"
(?IDENTITY#Transformable#SPK##2QBMB)
This is the code that produced those errors:
#include "Extensions/Emitters/SPK_RandomEmitter.h"
using namespace SPK;
int main()
{
RandomEmitter e;
e.changeFlow(6);
e.getFlow();
return 0;
}
So that's my problem, I'm sorry for explaining too much but I've done a three days search without finding any solution.
PS:
the library is very big, so an automatic solution is a must.
This is a very, very unfriendly C++ library to have to interop with. Scratch the idea that pinvoke can work, C++ classes require C++/CLI wrappers. There are a great many classes with many small methods. The library depends on composition to generate effects so any approach that tries to do the interop with a few God classes is a dead avenue.
The most significant hazard is that it heavily relies on multiple inheritance. Not supported in .NET, this will defeat any tool that auto-generate wrappers. Also note that it only supports OpenGL rendering, not a terribly popular graphics api on Windows.
The library is attractive, and has been around for quite a while, but nobody has successfully ported it to .NET yet. This is unsurprising. In my opinion, you don't stand a chance. Only a rewrite could work.
PInvoke is the way to do what you are looking for. Doesn't matter if you have or do't have the code for that DLL so long you know the function signature.
Have a look at these articles from MSDN and code project that cover basics of PInvoke:
Platform Invoke Tutorial
P/Invoke Tutorial: Basics (Part 1)
Edit:
There are tools that can possibly generate DllImport signature for you. I have NOT tried any of these myself. Have a look:
P/Invoke Signature Generator
Easiest way to generate P/Invoke code?
This one
http://www.swig.org/
Hope that helps.
If your native dll exports some classes, then I would strongly suggest creating another native DLL wrapper for the original one. It should export a few functions and no classes at all.
Exported functioned could be something like:
my_lib_create_context( void ** const ppContext );
my_lib_delete_context( void * const pContext );
my_lib_do_something( void * const pContext, T param1, T param2 );
Inside my_lib_create_context() create an instance of your class and pass the pointer back through the ppContext parameter.
Inside my_lib_do_something() cast the pContext to a pointer of your class type and use it.
Also, when writing your wrapper, pay attention to calling convention, because you will need to pass that information to the .NET world (I think stdcall is default if not explicitly defined).
EDIT:
Regarding that part on how to do it:
Create a new C++ solution/project, select DLL type. Then add .def file to that project. Add to that file this:
EXPORTS
my_lib_create_context #1
my_lib_delete_context #2
my_lib_do_something #3
Then add some header file where you will put function signatures like this:
typedef void * SomeContext;
extern "C"
{
int __stdcall my_lib_create_context( /* [ out ] */ SomeContext * ppContext );
int __stdcall my_lib_delete_context( /* [ in ] */ SomeContext pContext );
// TO DO: ... you get it by now...
}
Implement these functions in .cpp file. Once you are done, create a wrapper in C# for this DLL and use it.
Hmm P/Invoke call GetProcessAdress .. so importing ABI problem is so so..
http://www.codeproject.com/Articles/18032/How-to-Marshal-a-C-Class
here are your answer give credit to those guy
I have a legacy code implemented in C (not C++). I would like to be able to call a few methods in this C code from my C# code (on Windows). What would be the best approach to interface between the two language? Please note that the method in C is not stateless. We need to call two methods:
initialization() => this will initialize the data structure and load data from files into memory. This method will be called once.
ComputeSomething(parameters) => there will be several calls from C# to this method.
Note: These two methods actually call several other methods but these are only the two methods that we would like to expose to C# (the code is quite complicated, that's why we do not want to port to C#)
I have been able to import the c code into visual studio and able to compile the code successfully. I know that we can probably implement the C code as windows service but I am looking for a solution that allow us to call C method from C# directly. Any pointers is highly appreciated! (is COM interop related to what I am looking to do?)
Sounds like you can use P/Invoke for this. Check out this site for tips:
http://www.pinvoke.net/
Also, try searching SO for advice on P/Invoke and Google for
c# pinvoke calling c code
I don't have any technical examples at hand, but I have written some .NET code which called Win32 API's via P/Invoke. The tricky part is getting the method signatures correct when passing parameters. This might help you out there.
Recent version of Visual Studio allow you to write C++ code that can call unsafe functions but still interface with CLR managed code. They call this "Implicit PInvoke," or "C++/CLR." Check out the MSDN article "Using C++ Interop" to learn more.
Managed code can't call unmanaged directly, so you need wrapper functions to handle the memory management issues and to translate between .NET objects and the data structures of your application. From the link above, check out the section on "How to: Wrap Native Class for Use by C#."
Here is a solution. The solution allows to call C# function from C by decorating your function with [DllExport] attribute (opposite of P/Invoke DllImport).
https://sites.google.com/site/robertgiesecke/Home/uploads/unmanagedexports
C# code
class Test
{
[DllExport("add", CallingConvention = CallingConvention.StdCall)]
public static int Add(int left, int right)
{
return left + right;
}
}
C code
int main()
{
int z = add(5,10);
printf("The solution is found!!! Z is %i",z);
return 0;
}
Received an unmanaged C++ dll with instance functions which need to be called from my C#. need to write a wrapper C++ dll to bridge the C# and original C++ dll as suggested by experts here. it is new to me and want to learn from you.
Header file of the original C++ dll likes this:
class EXPORT_MACRO NB_DPSM
{
private:
string sFileNameToAnalyze ;
public:
NB_DPSM(void);
~NB_DPSM(void);
void setFileNameToAnalyze(string FileNameToAnalyze) ;
int WriteGenbenchData(string& message) ;
};
Start from a Class Library project template or CLR Empty Project template?
What's the wrapper code should look like?
Anywhere has step by step example for this?
thanks,
Oops, didn't read the question quite correctly. Check out this article, http://www.codeguru.com/Cpp/Cpp/cpp_managed/interop/article.php/c6867/
1) Need list of functions exported by the dll, which should be available in the header file.
2) Do DllImports for the functions you want to use
3) Marshal in/out parameters appropriately
This link should explain in more detail, http://msdn.microsoft.com/en-us/library/aa288468(VS.71).aspx