Is it possible to call C++ code, possibly compiled as a code library file (.dll), from within a .NET language such as C#?
Specifically, C++ code such as the RakNet networking library.
One easy way to call into C++ is to create a wrapper assembly in C++/CLI. In C++/CLI you can call into unmanaged code as if you were writing native code, but you can call into C++/CLI code from C# as if it were written in C#. The language was basically designed with interop into existing libraries as its "killer app".
For example - compile this with the /clr switch
#include "NativeType.h"
public ref class ManagedType
{
NativeType* NativePtr;
public:
ManagedType() : NativePtr(new NativeType()) {}
~ManagedType() { delete NativePtr; }
void ManagedMethod()
{ NativePtr->NativeMethod(); }
};
Then in C#, add a reference to your ManagedType assembly, and use it like so:
ManagedType mt = new ManagedType();
mt.ManagedMethod();
Check out this blog post for a more explained example.
P/Invoke is a nice technology, and it works fairly well, except for issues in loading the target DLL file. We've found that the best way to do things is to create a static library of native functions and link that into a Managed C++ (or C++/CLI) project that depends upon it.
I'm not familiar with the library you mentioned, but in general there are a couple ways to do so:
P/Invoke to exported library functions
Adding a reference to the COM type library (in case you're dealing with COM objects).
Yes, it is called P/Invoke.
Here's a great resource site for using it with the Win32 API:
http://www.pinvoke.net/
Sure is. This article is a good example of something you can do to get started on this.
We do this from C# on our Windows Mobile devices using P/Invoke.
The technology used to do this is called P/Invoke; you can search for articles on the subject. Note that it is for calling C from C#, not C++ so much. So you'll need to wrap your C++ code in a C wrapper that your DLL exports.
Have you considered Apache Thrift?
http://thrift.apache.org/
It seems like a very very neat solution.
Related
In VS C/C++ you could use extern "C" __declspec(dllexport) -function declaration-.
How do I accomplish this in a C# dll? Is there C# code equivalent to the above code?
Edit: More info
I am trying to create an add in for Notepad++ and I want to use C#, but the common way I've seen so far is to use legacy C++ code with the above call to export a few of the functions that Notepad++ expects to import and call. There is an example app using C#, but this still requires a loader DLL, which I assume from the comments/answers below is the only way for C#.
Unmanaged Exports =>
https://sites.google.com/site/robertgiesecke/Home/uploads/unmanagedexports
DLLExport => https://github.com/3F/DllExport
How does it work?
Create a new classlibrary or proceed with an existing one.
Then add the UnmanagedExports Nuget package.
This is pretty much all setup that is required.
Now you can write any kind of static method, decorate it with [DllExport] and use it from native code.
It works just like DllImport, so you can customize the marshalling of parameters/result with MarshalAsAttribute.
During compilation, my task will modify the IL to add the required exports...
I've seen people do this before, but it required ildasm, adding the MSIL .export directive, and then reassembling. A program named dll_tool can do these steps for you.
If you want to build a mixed-mode DLL with both native and managed exports, you should be using C++/CLI, which is specially designed for this purpose.
Yes, it is possible to export functions from a C# dll in much the same way that C++ does it! You need a little help from an add-in Unmanaged Exports (DllExport for .Net) that facilitates this process, or from a similar method such as Exporting functions in C#/VB.NET to native code.
Please see Code to Export C# DLL to Metatrader Build 600+ for a working example using Robert Giesecke's C# Project Template for Unmanaged Exports to export a C# dll to a legacy application (Metatrader) that has a great deal of similarity to C++.
Additionally, you might find Native and .NET Interopability interesting though it is mostly geared toward accessing native code from within .NET rather than the other way around.
No, you cannot do that in the same sense as you do in C and C++.
But you can create COM API to achieve that which then you can use in C and C++ code.
See these articles
C# Classes as COM Objects
Calling Managed .NET C# COM Objects from Unmanaged C++ Code
COM Interop Part 1: C# Client Tutorial
i'm exploring the idea of use .net as a scripting language for my program.
i found a lot of examples on internet that shows how to host .net and then, from c++ call functions from .net.
But i need to go on the other way too, from this code in c#, i need to be able to create/call c++'s objects from this c# script, so i need to expose functions/objects to control it from C#.
How can i do it?
Simple Example to show what i'm talking about
I call my c++ method "CreateGUI". It'll call .net code: "InitializeGUI", and this "InitializeGUI" need to check if an object (for example, the texture) is instantiated inside C++.
Can someone help me?
Thanks!
If you use managed C++, you can create a managed C++ component which can be called from your C# code. If you use unmanaged C++, you can either create a C++ COM component and use it through C# via RCW (Runtime Callable Wrapper) mechanism or you can create a C++ dll and call it from C# via PInvoke.
You might also investigate Mono, which is explicitly intended to be embedded and will run any compiled .NET assembly, meaning the full powers of C#, VB.NET, even F# will be available.
I have zero experience in C++, but have a few years C# experience.
Are there an examples out there showing how I can create a method in a C++ program which is then called from a C# program using the DLL?
Cheers
Using p/invoke, you can call C++ code from C#.
Read this: Calling Win32 DLLs in C# with P/Invoke
Another small yet good article : Using P/Invoke to Access Win32 APIs
--
EDIT:
This aritcle explains how to create a DLL library in C and then use it with C#
You can also try compiling the C++ code in Visual Studio to VC++, which is plain old .NET. Avoid the p/invoke, if the code is compatible.
Create some function in C++ with "extern "C"" to avoid the c++ name mangling and then use PInvoke as suggested by Nawaz is the better way.
In the course of finding a way to interoperate between C# and C++ I found this article that explains about P/Invoke.
And I read a lot of articles claiming that C++/CLI is not exact C++ and requires some effort to modify from original C++ code.
I want to ask what would be the optimal way when I have some C++ objects (code/data) that I want to use from C# objects.
It looks like that in order to use P/Invoke, I should provide C style API. Is it true? I mean, is there a way to export C++ object to C# like SWIG with P/Invoke? Or, do I have to use SWIG for this purpose?
How hard is it to change C++ to C++/CLI? Is it worth trying compared to rewrite the C++ to C#? The C++ is well designed, so implementing it to C# is not great deal.
(Off the topic question) Is there the other way round? I mean, if I want to use C# code from C++, is there any way to do so?
I would not recommend rewritng your C++ library into C++/CLI. Instead, I would write a C++/CLI wrapper that you can call from C#. This would consist of some public ref class classes, each of which probably just manages an instance of the native class. Your C++/CLI wrapper just "include the header, link to the lib" to use the native library. Because you have written public ref class classes, your C# code just adds a .NET reference. And all you do inside each public ref class is use C++ Interop (aka It Just Works interop) to call the native code. You can apply a facade while you're at it if you like.
The C++/CLI syntax is awkward, but it does allow you to expose managed objects from C++ code. This can be convenient if you have a large C++ API and can abstract some of that functionality to a simpler interface for consumption by your managed code. I've done this successfully for integration with tools like the Matrox vision library, where I could write my vision analysis code in C++ and then use the C++/CLI extensions to expose high-level managed classes. The most painful part is probably string and array inter-op, but strings have always been painful, even in plain C++.
C++/CLI can definitely consume any .NET managed objects, but you have to take special care if you're using any pointers to managed memory (you'll need to use pinning in this case.) If I need to pass pointers to an API, I usually prefer to keep that memory unmanaged and then create managed wrapper classes for manipulating the unmanaged memory.
Further to Kate Gregory's answer, to call C# code from C++, using C++/CLI is the obvious way to do it, as it makes it extremely simple and seamless.
Wrap your C++ native classes, as pointer to implementation, into C++/CLI classes, then call & use these CLR-based classes by 'using'ing them in your .net application. This is my recommended way. DO NOT REWRITE your existing classes in C++/CLI.
In my project I got a device which comes with C++ Sample codes. The codes are ok and the device is working as expected.
But I need it to talk with my C# interface because all other devices are currently using C# interface.
So I am planning to create a DLL Wrapper for the driver. I will create a C++ Library of my own (from source code with proper interface) and Call this C++ Library from C# using DLLImport (just call my interfaces there.).
I am pretty sure it can be done this way, but I have never created a C++ Library and used it from C# yet. So, can anyone refer me to some tutorial that goes with my problem?
I am using C++/C# int VS.NET 2008.
Regards,
Maksud
Have a look at
using a class defined in a c++ dll in c# code
Another useful tool you have at your disposal is C++ CLI.
You can use C++ CLI to create an intermediate library - one that exposes managed classes but runs unmanaged C++ code. You can actually mix managed and unmanaged C++ in the same DLL.
The unmanaged portion can accesses the unmanaged DLLs without having to use the PInvoke functions.
Your C# code can access the managed classes in this intermediate library.
Depending on the DLL and what you need to do you may not need to create a wrapper directly. You might be able to get away with P/Invoke for the functions. You will need to evaluate your specific needs and what is already available in the libraries/code provided.
For anyone who comes to this question and are looking for answers, you may want to try xInterop NGen++ , a C# wrapper generator for native C++ DLL, which has been just released to the public, the tool can generate C# wrapper for native C++ DLL automatically and instantly by using advanced P/Invoke technologies. Check out the current version and a free version will be out soon.
(I am the author of the tool)