Has anybody out there used the SWIG library with C#? If you have, what pitfalls did you find and what is the best way to use the library? I am thinking about using it as a wrapper for a program that was written in C and I want to wrap the header files where I can use them in my .NET application.
Edit: Some clarification on target OS's.
I plan on running the application on Linux and Windows, therefore the reason I am looking into SWIG. P/Invoke is not an option.
For my last project, here's the entire C# SWIG configuration file:
%module mdProject
%{
#include "mdProject.h"
%}
I compiled it in SWIG with:
swig -csharp -c++ -I../../Include mdProject.i
This generated a Project.cxx which I compiled and linked directly into the 'main' DLL, so I didn't need a second C++ 'helper' DLL. SWIG also generated a bunch of C# files which I compiled into a .NET DLL. My other wrappers (Java, PHP, etc) do use a helper DLL.
As #patrick mentioned, SWIG uses P/Invoke, so if you have a problem with that, you'll need to find another solution.
If you use types that stray from the ordinary (voids, structures, etc), you will have to do some extra work to get it right, but for the average API using int's, char*'s etc, it's fine.
I think the mistake the earlier posters did was read the docs and not look at the examples.
A few hours ago I needed to interface some C++ classes to C#. I looked in my Swig dir (I already had it for other work), found the directory Examples/csharp/class, browsed the code, loaded the solution, grokked it, copied it, put in my code, it worked, my job was done.
With that said, generated P/Invoke code isn't a solution for all needs. Depending on your project, it may be just as simple to write some simple API wrappers yourself or write managed C++ (Look up SlimDX for a superb example of this).
For my needs, it was simple and easy - I had mystuff.dll, and now in addition I can ship mystuffnet.dll. I'll agree that the doc is difficult to get into.
Edit: I noticed the OP only mentioned C. For that, you don't really need Swig, just use the usual C#/C DLLImport interop syntax. Swig becomes useful when you want to let C++ classes be invoked from C#.
I did attempt to use SWIG to wrap a project C++ for using in .NET a few years ago.
I didn't get very far as it was a massive giant pain to produce the configuration that SWIG required. At the time I just wanted a solution, not to learn another language/api/etc. SWIG may be easier to use these days, I couldn't tell you.
We ended up using Managed C++ to wrap the C++ project. It worked really well.
If you're just invoking functions straight out of a dll, I'd suggest not worrying about either of the above, and just using P/Invoke
Related
Clarification. There is a C++ exe and a C# exe. The C# exe is a wrapper for a C# dll. I need the dll to call a logger function in the C++ code (so that only one log file is produced). Currently there is a c++/CLI bridge which allows the C++ exe to call methods in the C# dll.
Apologies if this is a poor question. Its possibly a case of I just don't know what to search for / results for what I am searching for isn't of much use.
I have an application written in C++. It calls a tool written in C#. It appears the executable for the tool is just a wrapper for a c# dll.
The tools purpose is to analyse and display data. The main application calls it for example to have it open a new file. The tool has never had to call anything in the C++ code before so this has always been one way. It appears to be implemented via a C++/CLI bridge. The bridge calls the functions in the tool api.
It is now required for the tool to call some methods in the C++ application. I have no idea how to go about implementing this. My c# / C++/CLI experience is somewhere between poor and non-existent. I started by attempting to clone the C++/CLI bridge and "reverse" it, but since the C# code is in effect a library calling it from the bridge is fairly simple.
However, i'm not really sure (if its even possible) how to call the C++ application from a bridge.
So far the only workable solution I can think of is to have the c# code output to a file (or hopefully shared memory) then the c++ code check it periodically. This isn't close to ideal.
Any advice would be appreciated.
Thanks
Ok, i think i'll throw in a suggestion here.
Depending on what your goal is:
1) Goal: execute some of your c++ logic from c# code.
Solution: this one is fairly simple. You extract logic of interest into separate C++ project, build it as a library and then use it in both applications. As you said, there are plenty examples on how to call c++ dll from c# code.
2) Goal: froce your c++ application to execute some of it's logic from C# application.
Solution: it all comes to setting up an interprocess communication. There are quite a few approaches, that are listed here. I suggest using NamedPipes but you are free to pick w/e you are comfortable with.
Edit: Judging by your edit you probably want the second solution.
My question is what's the best way to create an inteface with C++ code.
Basically so far I have a console project in c++, that works as I expect to, but I now want to make a GUI for it. The choices to me seemed to be:
Make a dll of the c++ project, and then make a C# form which uses the dll to do the logic.
Same as 1 except with VB.
Use QT or something eqvilent and make the inteface in the same project.
I've been trying option 1 for quite sometime. I made the library I believe successfully by making a library project in Visual Studio 2005. I then put it in my c# project but I then had a problem of being able to instantuate my class, but the c# project couldn't see my methods.
The only fix I could find to this was to use the ref keyword. The problem with this was then not being able to mix managed and unmanaged code and trying this on one of the larger classes produced about 250 errors.
Option 2 i had the same problem with.
I'll start option 3 if I have to, I just wondered if I was missing anything fundamental or any suggestions in general?
Cheers for reading.
You absolutely can use C++ code from C#, but if it's unmanaged C++ code, you have to delve into the realm of pinvoke to call your code.
If you're attempting to leverage an existing C++ library from .NET, one of the easiest ways to do this is by using C++/CLI as a wrapper around your unmanaged library. C++/CLI compiles into .NET bytecode, but features lots of automatic unmanaged interop. A phrase that's often floated about when using C++/CLI unmanaged interop is "it just works". It's an accurate phrase.
Once you have a C++/CLI wrapper for your unmanaged code, C# should be able to see everything exposed by your C++/CLI library.
I have a (header only) C++ library that I am looking to port to C#. It is a wrapper of the win api which I have made for a certain purpose. I want to port it to C# because I want to develop it further using C#. What is the most efficient (and easiest?) way to port it. Please note that I do not want something hectic because I don't want to spend more time porting the library than it took to make that library in the first place. So is there a way?
It depends very much on how big your lib is, how it is structured, how your memory allocation looks like, how much you made use of libs not available in C# (like the C++ std lib), how much C++ template programming you have used etc.
Different strategies may be
try to port (parts of) it automatically by some code generator of your own
do not port it to C#, instead use C++/CLI (something I did very successfully in the past)
do it manually because the C++ concepts you have used so far don't map well to C#
"Header only" does not seem to make a real difference. In fact, things may technically get a little bit easier when you have just one C++ file for each class to be ported to one C# class file.
A couple of ways I can think of.
Manual conversion to C# dll with possible code generation help of T4.
Change your c++ library to a managed dll so you can use it in your c# project.
Of course, you might use interop with your c++ library in your C# project. But in that case, I am not sure about purpose of your c++ library since you said it's a wrapper.
Since you already have c++ library that you can fully control, I would try to go with #2 first.
I need to create a VC++ wrapper in C#. Is there a way to automatically generate the code?
Edit: let me clarify a bit: I have a simple project with complicated math functions (computing magnetic declination) in c++. Its just three files, one header, one command line controller and the library.
I was looking at SWiG but I found it to be enigmatic :P. I'm taking a look at C++/CLI.
Any tips and pitfalls to watch for?
Take a look at: Using Unmanaged C++ Libraries (DLLs) in .NET Applications
Or you can use C++/CLI
SWiG supports C#. But a C++/CLI wrapper will be much more ".NET-like" than one automatically generated by SWiG.
You can have a look at this tutorial:
http://www.codeguru.com/csharp/csharp/cs_data/article.php/c4217
I think it's better if you make your own wrapper than using any tool (if it does exists). The reason is that you can create a better C# wrapper using the right philosophies instead of generating a list of function call from a DLL.
And for the pitfalls, the only thing I can say is that since you are going to mix manage and unmanaged class, be sure that your struct/parameters are matching (sizeof or types).
As for most short questions: It depends on your settings and requirements! ;-) If you have a more C style interface, you might be able to solve your problem just by using Interop. If "real" OO progamming and C++ are involved, you probably have to look at C++/CLI. That can be easy, but it can also become painful - depending on your classes. As far as I know, there's not automatic code generation tool.
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++