I have the c++ source code of functionality which is appealing to me.
What effort/work is involved/required in order to either reference this from a .net application or build this code as a .net assembly (preferably c#)?
This is my first attempt at porting code, so please breakdown your answer for me step by step.
There are several ways of doing it.
PInvoke
Create C++/CLI wrapper around your C++ native code (make static library out of C++ native code) and C++/CLI generated assembly can be easily utilized in .net application.
COM, i.e using interop (which is difficult among all the options)
In my suggestion easiest way is to use option 2, but you need to take care of proper marshaling.
Solution A:
If you have the source code, then compile the CPP program as a DLL file.
Use P/Invoke
Solution B (if the functionality you want is in a static library):
Create a stub function caller and compile THAT as a DLL
Same as solution A.2
Related
I'm noob in C# and I already searched on the web. Anyway I'm still not sure about this and I do not have the total control of the code I have to implement, this is why I would like to be sure I needn't make any dll. I have a C++ file with a method, and I want to call this method from C# code. I just added "extern C" to the function.
When I just add the .h and .cpp files to the C# project they aren't detected. And of course, when I try to add it as reference, it doesn't work.
So do I absolutly have to make a dll ?
Your options for accessing the C++ code from C#:
Compile C++ as unmanaged DLL and access using p/invoke. This requires the C++ code be exposed using a C style API.
Compile C++ as unmanaged DLL and access using COM. This requires that you wrap your C++ in as COM objects.
Compile C++ as mixed/mode C++/CLI assembly and access the assembly as a managed reference. This requires that you wrap the original C++ as managed C++ ref classes.
All of these options, by necessity, involve the creation of another module/assembly. You cannot link the C++ code directly into your C# assembly.
You might like to try using the PInvoke Interop Assistant to generate the C# necessary to interact with the DLL via Platform Invoke. Be aware that this is imperfect though so YMMV.
Another alternative, if you have the knowledge and patience, is to make a COM component out of your native C++ DLL and consume that from C# by using the Type Library Importer to create a managed wrapper.
You won't be able to interact with .cpp/.h files since you need at least a binary object (assembly) for C# to interact with and C# won't generate any binaries from .cpp/.h. That's on the subject about adding these files as references to the project.
As for the argument that you don't have control over the code - well, don't make a DLL out of the actual .cpp/.h, but make your own thin DLL that has a wrapper object that just includes the headers, calls whatever method you would be calling and links to the appropriate .o files or .lib or whatever you have. If the interface changes you would just changed your thing wrapper which should be easy.
I am working on a project. In that C++ code is referencing to a Class Library which is written in C#. I want to pass Object of C++ Classes to C# Class library.
So Is this possible, If yes please let me know how ?? otherwise I will have to pass around 100 arguments to C# Class Library.
Regards,
Vivek
you shoul use marshling.
Marshaling is the process of creating a bridge between managed code and unmanaged code; it is the homer that carries messages from the managed to the unmanaged environment and reverse. It is one of the core services offered by the CLR (Common Language Runtime.)
namespace System.Runtime.InteropServices.Marshal
Read here a good blog about marshling
If you have this option, you can add a cpp file to your project that will be compiled with enabled CLR (managed C++). From managed C++ you can call C# classes. You can find and example here:
Managed C++ to form a bridge between c# and C++
Another option is to create a managed C++ dll as a bridge between C++ and .NET if you don't want to enable CLR in your calling native application. I used this trick and it worked fine but be aware that once you load that bridge dll library, CLR is loaded in memory and your process gets "infected" by CLR. You will have that effect anyway though.
I am trying to read GUID attribute of a C#.net assembly from c++ (VC++ 10).
I should mention that, I don't want to use .net or .net reflection. looking for a pure c++ way.
what is the solution ?
Thanks in advance.
You need to use the Unamanaged Metadata API
and especially the IMetaDataImport::EnumCustomAttributes Method
That's going to be quite a work... Here is a link that gives a good starting point on this (it's C#, but the ideas are exactly the same, and is in fact easier to program in C++): Reading types from assembly
Check out the The .NET File Format MetaSection over at CodeProject.
i understand you don't want to use reflection or .net.
You do however want to get the GUID from a C# dll you have, that was built with .NET.
The common way C# developers make their class libraries available to COM-based developers is to use the tlbexp.exe (type library export) tool to export a type library file.
The COM-developer can then use the .tlb file in their COM code.
When the C# developer builds the dll they either put the Guid manually in the AssemblyInfo level (in .NET) or the compiler will generate the Guid automatically when building the dll.
show how the COM client (C++) is built to use the COM server (C#)
http://msdn.microsoft.com/en-us/library/aa645738%28v=vs.71%29.aspx
note that in this article refers to another tool regasm.exe which registers the dll and can export the tlb at the same time but it is not necessary to register the dll on your system
as a developer you can just use the tlb file
How would I export functions defined in a C# class library, while enabling them to be imported to and called from an unmanaged C++ application/DLL ?
Strictly speaking, you can't just export functions as you would in a classic .dll, as .NET .dll's aren't really .dll's at all. Your only three options are:
Use managed C++
Expose your C# classes as COM objects and consume them from your C++ code
Host the .NET runtime in your C++ project and interact with your C# classes through that.
Your C++ Apllication would have to start by hosting the CLR. There is nothing special required from the .NET DLL.
You would not. Not supported. You can pretty much only export COM objects from a C# class librarly.
You could also make a C++ wrapper for your C# library - a simple Managed C++ DLL that would import .NET methods and export them natively. This adds an additional layer, but it might be useful if C# library is a must have.
Another option is to tweak the compiled assembly to export the functions. A C# compiler cannot do this, but it takes a slight change of MSIL code to get the things done.
Have a look at this article - there're some links on how the stuff works, and a tool to automate it (though I haven't tried it myself).
I want to add a VC++ DLL reference into my C# Visual Studio project. But when I try to add it I see, "It is not a valid assembly or COM component".
Please suggest how I can use the VC++ DLL as a reference in a C# project.
There are two options for using a C++ DLL from C#: either COM interop, or P/Invoke. COM Interop involves creating a COM object in your C++ DLL, and then adding it as a reference. You can use the COM object like a C# object (for the most part) at this point.
P/Invoke allows you to call exported functions from C# (think calling standard Win32 API functions from C#). This is likely easier to set up, since all you need to do is export a function, however that could cause you to refactor your code in the C++ DLL, since it's not a very OOP way of doing things.
You can only use C++ components in C# when they have been prepared for use, for example by being written in C++/CLI or being written as a COM server.
If your component is a plain C++ dll you'll need to write some wrapper code, probably best is C++/Cli
I am not sure whether this solve..
run:
tlbimp /out:MyOldCom.dll MyNewAssembly.tlb
Then use it as you would any other assembly.
Please refer
http://msdn.microsoft.com/en-us/library/aa302324.aspx
http://msdn.microsoft.com/en-us/magazine/cc301501.aspx
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One way is to package your DLL as a COM class and Another way is using DllImport