I need to do some process injection using C++ but I would prefer to use C# for everything other than the low level stuff. I have heard about "function wrapping" and "marshaling" and have done quite a bit of google searching and have found bits of information here and there but I am still really lacking.
Things I have read in order of usefulness;
http://msdn.microsoft.com/en-us/library/ms235281(VS.80).aspx
http://www.drdobbs.com/cpp/184401742
http://geeklit.blogspot.com/2006/08/calling-c-lib-from-c.html
How can I wrap all the lower level stuff (native C++) in C# so I can easily command those functions in a language I am more comfortable with, C#?
Any information on the topic is much appreciated.
I think P/Invoke is really the most straightforward approach:
Create a DLL in unmanaged C++, containing all the functionality you need to do the injection.
In your C# code, declare some static extern methods, and use the DllImport attribute to point them to your C++ dll. For more details, see the link provided by arul in his answer.
Note that P/Invoke isn't limited to "windows API functions" — you can call functions exposed by any native DLL.
A potential downside of P/Invoke is that you will have to provide the signatures for your C++ functions, possibly specifying some less-than-obvious marshalling. In that case, you could consider constructing a COM server instead of a "plain" DLL, and using COM interop to call your code from C#.
You want to use P/Invoke, see MSDN Magazine.
If Pinvoking isn't what you want to do, then create a managed C++ application. Use native C++ to do the process injection stuff. Use managed c++ to create a .NET friendly interface to this native behaviour. This can then be called from C#.
Related
I'm trying to read AAF files (that describe edited video and audio sequences) in c#. AAF is open source, and there's a C++ SDK available http://sourceforge.net/projects/aaf/.
I'm a C# coder and while I understand some of the C++ coding paradigms, my C++ is basically non-existent.
I presume the intereaction is possible using pinvoke which I've used before for interacting with Win32. With win32 I've pulled calling information from pinvoke.net, but I'm not entirely sure how I go about defining the pinvoke entry points from scratch with a third party SDK.
Can anyone help me to get started on this? For instance, what are the first steps in pinvoking a third party C++ library? Are there tools for helping automate this process?
You have basically two ways of doing that:
Using C++ Interop (implicit PInvoke)
Visual C++ can interop with native C++ code. So you can use Visual C++ as a bridge between the native C++ and C#. Basically you have to write wrapper (or "proxy") classes in visual C++ to interact with your native C++ objects.
Under the hood, this method uses PInvoke (therefore "implicit PInvoke") with specific options, but it has the advantage of retaining the object-oriented structure of the native C++.
Note that this method is not portable to Mono.
Using good ol' PInvoke
You can use PInvoke with C++ the exact same way as you use PInvoke with C.
There is however a limitation: you cannot PInvoke C++ methods this way, so you lose the C++ object-oriented structure.
If the library that you are using provides a C API, you can use that. Otherwise, you have to create a small C++ wrapper that will wrap the C++ API in the form of C-style free functions.
If you have a lot of classes to wrap this way, you can use SWIG to wrap automatically. As a bonus, SWIG recreates the object-oriented structure in C# via some guru code generation. However using SWIG requires some setup and I don't think it is necessary if you only need a few functions.
Is there a way to call c# dll from c++ unmanaged application without COM usage?
You can do this using Reverse P/Invoke - example and discussion here.
It is actually possible to disassemble, modify the IL, and reassemble it with exported functions. I messed with this a few years ago, and created an application that would disassemble a dll, provide a list of functions that could potentially be exported - allowing the user to select them, then re-write the IL and reassemble everything. Then, I could call directly into the dll from unmanaged code...or p-invoke into the dll from managed code (not really practical, but interesting nonetheless).
Surely there is a reason that this isn't supported in the .net languages themselves (even tho it is supported in MSIL). I wouldn't use this in production:
Dead link:
http://www.csharphelp.com/2007/03/exporting-managed-code-as-unmanaged/
Wayback Machine:
https://web.archive.org/web/20140213030149/http://www.csharphelp.com/2007/03/exporting-managed-code-as-unmanaged/
I might be a bit late, but check this out.
Using this little msbuild task, you can create a C# library that can be called as if it were a native DLL. (e.g. write plugins for apps that require them to be native dlls)
Oh and don't forget to use the project template, which will setup everything for you.
Your only option really is to either use C++.net or create a C++.net wrapper for it that exports what you need.
Calling C# code from C++
I was wondering if I can use a library -written in C++- in C#
The problem is that library has its own structures and classes..
Will I be able to use it in C#?
Thanks
EDIT This library is open source..
so if my requirements needs something special in C++ code, I will be able do it...
You cannot directly use C++ classes in managed code. The chief problems are not being able to use the same memory allocator as used by the C++ code and not being able to invoke the constructor and destructor easily. A Microsoft employee posted a blog post to show that it is not impossible. I would not recommend doing this.
COM is a solution but that invariably requires a fairly big rewrite and good COM programming skillz. A managed class wrapper in the C++/CLI language is usually the best solution. You could take a peek at the SWIG tool to consider auto-generating those wrapper classes. Beware however that this tool can easily create more problems than it solves.
There are two ways, both using an Adapter (which maps C++ classes to .NET classes):
C++/CLI
COM
The former avoids going via COM, and much of the C++ code might be able to be just compiled with the correct switches.
Additional: In theory P/Invoke might be possible, but all the C++ semantics would be lost, you would need to handle C++ object lifetime manually (and instance references as IntPtr). Plus of course you would need to call the mangled names...
Another option is to write a managed wrapper in C++/CLI. I prefer that instead of using P/Invoke.
I am an experienced .Net programer, but have not compiled a C/C++ program in my life. Now I have this C-dll, headers and documentation (3rd party, not from Win API), from which I need to call about ten methods.
I was thinking of using Platform Invoke. I found these three tools that would create the code for me:
PInvoker: http://www.pinvoker.com
P/Invoke Interop Assistant: http://www.codeplex.com/clrinterop
P/Invoke Wizard: http://www.paulyao.com/res/pinvoke/pinvoke.aspx
and possibly
Swig: http://www.swig.org/
Pinvoker seems to have a bit different approach than the Interop assistant and the Wizard. Swig I just found when checking that this question has not been asked here.
What are the pros and cons of these tools?
What would be the best = easiest and safest way for me to produce the P/Invoke code given that I don't know much about C/C++?
See http://dotnetperls.com/dllimport-interop for an interop example, and this MSDN article for more info. The bible for this stuff is Adam Nathan's book.
Basically you will need to identify the functions in the DLL you want to call. These need to marked with extern to make them accessible to the outside world. The next step, which can get tricky is writing a DllImport for the function. This needs to map between the managed and unmanaged worlds. You will need to work out how to marshal any complex data structures from the C dll into managed code.
You should check to see if there is any sort of COM interface to the DLL. Make sure you really need to use P/Invoke first.
SWIG was originally for wrapping C/C++ code for use from scripting languages. It generates C# code from an interface description (see tutorial). I wouldn't recommend using it from C# if P/Invoke is an option.
if the signatures of the functions are simple then it should take 10 minutes to setup - ie if they take 2 char * and return an int. Its only once they get complicated that it gets messy
The bible on pinvoke is Adam Nathans - .NET and COM: The Complete Interoperability Guide
And I agree with other poster - swig is not the right thing
Is it possible to use a C++ .lib file from within a C# program?
There are plenty of ways. Read about "interop" in MSDN..
One way is to expose the lib as a DLL, and then use pinvoke to call these functions from a C# project. That limits you to a C-style interface, though.
If your interface is more complex (e.g. object oriented) you can create a C++/CLI layer that will expose the lib's class structure to your C# program. This means you'll have to create a managed C++ (or C++/CLI as it's now called) project; then design an interface in managed code that will be implemented by calls to native C++ (i.e. your lib).
Another way of doing this is by wrapping your lib with a COM interface. But COM's a pain, so I wouldn't...
Not directly. You can create a C++/CLI assembly that consumes the lib and then access that from C#, or you can wrap the lib as a DLL.
What you need is a managed wrapper (C++/CLI) around the native C/C++ library that you are working with.
If you are looking for any C++/CLI book I'd recommend Nishant Sivakumar's C++/CLI in Action
Already answered to wrap it but here's an example . Good luck!
I would take a look at swig, we use this to good effect on our project to expose our C++ API to other language platforms.
It's a well maintained project that effectively builds a thin wrapper around your C++ library that can allow languages such as C# to communicate directly with your native code - saving you the trouble of having to implement (and debug) glue code.
No. You can only use a full .dll from a C# program.
That depends, do you have any limitations on this scenario?
If you have a lib file, it should be possible to first compile it into a DLL file, secondly exposing the functions you want to call in the DLL interface, and thirdly, call them using C# native methods (have a look at pinvoke.net on how to do this bit).
you can't use a lib, but like the others said, you can use it if you wrap it into a dll.
swig can take the headers of your .lib, and if they are not too complex it can generate the dll for you which you would then call with a pinvoke from c# which would also be generated by swig.
if your library is complex and has reference counted smart pointers everywhere, you should find an alternative.