I have a DLL made in C#, this DLL contains some clases like Creator.
I need to load this DLL and use Creator class in C++ unmanaged,
so Is there some way to create that instance or must I load just the functions exposed?
I need something like this:
CreatorInstance->Init();
Is this posible?
Most of what you need can be found here: http://msdn.microsoft.com/en-us/library/x0w2664k%28VS.80%29.aspx
Primarily, you need to learn about the /clr switch for C++ compilation. Then you need to understand the C++ extensions that Microsoft added to allow for mixed assemblies. (A C++ "pointer" to a managed class would use p^ instead of p*, and so on.)
John Fisher's approach using C++/CLI is by far the easiest means of handling this, but it is not the only means.
The other three options are:
1) Use COM interop to wrap the .NET class via COM
2) You can host the CLR in your native, unmanaged application, and call into it. For details, see this article.
3) You can host the Mono runtime, and use it to call your managed code. For details on this, see this page.
Option 2 and 3 are very similar, but IMO, 3 is easier than 2.
Here is an interesting article on how you should be able to accomplish this without using the /CLR option
http://www.codeproject.com/KB/cs/ManagedCOM.aspx
Works pretty well.
First of all, it is possible and you do not "have" to use CLI or the /clr switch. Using the good old COM architecture you can do it pretty easily http://msdn.microsoft.com/en-us/library/zsfww439.aspx. Understanding the way COM works might be the biggest challenge here, but it's usefull once you know it.
Related
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++
I'm just looking for a best way to re-use code written in c#, in my c++ projects. Creating a com\service doesn't look like a best option for my needs. How difficult it is to export c# code into a dll and use it in c++? can i get some suggestion or example? is this usual requirement or ? Please help me.
i use win7, VS2008, win7sdk
Thanks & Rgds, ~calvin
Executing managed code from an unnamaged executable is possible, though not quite easy. You can look into this article for an introduction and this book to go further.
I personally would avoid this kind of things in most cases and, if possible, switch the C++ project to C++/CLI to obtain an immediate compatibility with .Net assemblies for a minimal cost.
You can't export C# code into a native dll afaik. At least without very much pain in your buttocks. You should have thought beforehand and write the reusable part in C, thus creating a native DLL which could be used from all languages.
Also, you could try managed C++ - I personally hate it... but there you go
In case you need to use code written in C# C++, then you need to first see what all data types you would be passing from your C++ code to C# code.
1. Basic data types like int, enum etc can be passed from unmanaged to managed code.
2. in case you want to pass on class object, than you need to use marshalling.
If you can't use COM (if the .NET code is already written for example), then you can host the CLR, but this is a long road...
See these other articles
How to load CLR into process and Create a C# DLL That Can Be Imported in a Delphi App Using stdcall - Possible?
Thus far I've figured out out I needed to recompile the library as a .dll instead of a .lib, enable /clr and /EHa instead of /EHsc. Now I've got a managed dll which I've added as a reference in my C# project.
Now how do I use it?
I'm prepared to write some wrappers, but I don't know where to begin or how to "see" what functions I've gained access to. I've read a little bit about how the class names and functions might be mangled by the compiler... do I need to go back and add __declspec exports everywhere (if so, how?), or is there an option in VS2010 that says "don't mangle it!"?
The C++ library in question is still under active development, so I'm hoping I can modify the C++ library as little as possible and just recompile it periodically with a few switches, and then expose the new functionality as I need it.
If you are going to compile your C++ (if originally was unmanaged C++) you will need to do much more than just add the /clr switch. In order for C# to use the DLL you will need to create managed classes and other types based on CTS which are compatible with C# (.NET).
See and ref classes.
A good book to read about the subject (IMHO) is this one
You can either expose the functions as C style functions (i.e., no mangling) from your dll or you can expose them as COM objects.
I'd suggest writing a COM wrapper, and using that instead. Have a look at http://msdn.microsoft.com/en-us/library/035x3kbh%28v=VS.80%29.aspx for intro instructions. You'll want to make your object interfaces derived from IDispatch and be automation compatible, which should enable the runtime to consume them without any custom marshaling.
A nice benefit of this approach is you can continue to build your native code as a library, and just make your COM project use it. Also, it's still native code inside the COM object, so there's much less potential for unknown problems (once you get the interface layer working).
That's my suggestion, anyway.
Yes, wrap it in à COM object. I believe ATL is what you meed to do this with the least effort.
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.