I have a legacy code implemented in C (not C++). I would like to be able to call a few methods in this C code from my C# code (on Windows). What would be the best approach to interface between the two language? Please note that the method in C is not stateless. We need to call two methods:
initialization() => this will initialize the data structure and load data from files into memory. This method will be called once.
ComputeSomething(parameters) => there will be several calls from C# to this method.
Note: These two methods actually call several other methods but these are only the two methods that we would like to expose to C# (the code is quite complicated, that's why we do not want to port to C#)
I have been able to import the c code into visual studio and able to compile the code successfully. I know that we can probably implement the C code as windows service but I am looking for a solution that allow us to call C method from C# directly. Any pointers is highly appreciated! (is COM interop related to what I am looking to do?)
Sounds like you can use P/Invoke for this. Check out this site for tips:
http://www.pinvoke.net/
Also, try searching SO for advice on P/Invoke and Google for
c# pinvoke calling c code
I don't have any technical examples at hand, but I have written some .NET code which called Win32 API's via P/Invoke. The tricky part is getting the method signatures correct when passing parameters. This might help you out there.
Recent version of Visual Studio allow you to write C++ code that can call unsafe functions but still interface with CLR managed code. They call this "Implicit PInvoke," or "C++/CLR." Check out the MSDN article "Using C++ Interop" to learn more.
Managed code can't call unmanaged directly, so you need wrapper functions to handle the memory management issues and to translate between .NET objects and the data structures of your application. From the link above, check out the section on "How to: Wrap Native Class for Use by C#."
Here is a solution. The solution allows to call C# function from C by decorating your function with [DllExport] attribute (opposite of P/Invoke DllImport).
https://sites.google.com/site/robertgiesecke/Home/uploads/unmanagedexports
C# code
class Test
{
[DllExport("add", CallingConvention = CallingConvention.StdCall)]
public static int Add(int left, int right)
{
return left + right;
}
}
C code
int main()
{
int z = add(5,10);
printf("The solution is found!!! Z is %i",z);
return 0;
}
Related
I need to be able to invoke arbitrary C# functions from C++. In-process Interoperability suggests using ICLRRuntimeHost::ExecuteInDefaultAppDomain(), but this only allows me to invoke methods having this format: int method(string arg)
What is the best way to invoke arbitrary C# functions?
There are several ways for a C++ application to invoke functions in a C# DLL.
Using C++/CLI as an intermediate DLL
http://blogs.microsoft.co.il/sasha/2008/02/16/net-to-c-bridge/
Reverse P/Invoke
http://tigerang.blogspot.ca/2008/09/reverse-pinvoke.html
http://blogs.msdn.com/b/junfeng/archive/2008/01/28/reverse-p-invoke-and-exception.aspx
Using COM
http://msdn.microsoft.com/en-us/library/zsfww439.aspx
Using CLR Hosting (ICLRRuntimeHost::ExecuteInDefaultAppDomain())
http://msdn.microsoft.com/en-us/library/dd380850%28v=vs.110%29.aspx
http://msdn.microsoft.com/en-us/library/ms164411%28v=vs.110%29.aspx
https://stackoverflow.com/a/4283104/184528
Interprocess communication (IPC)
How to remote invoke another process method from C# application
http://www.codeproject.com/Tips/420582/Inter-Process-Communication-between-Csharp-and-Cpl
Edit: Host a HTTP server and invoke via HTTP verbs (e.g. a REST style API)
Compile your C++ code with the /clr flag. With that, you can call into any .NET code with relative ease.
For example:
#include <tchar.h>
#include <stdio.h>
int _tmain(int argc, _TCHAR* argv[])
{
System::DateTime now = System::DateTime::Now;
printf("%d:%d:%d\n", now.Hour, now.Minute, now.Second);
return 0;
}
Does this count as "C++"? Well, it's obviously not Standard C++ ...
See DllExport.
IOW: The exact opposite of how DllImport works.
https://github.com/3F/DllExport
It has support for Windows, with cross-platform support in the works.
C# code (which we call from C++):
[DllExport]
public static int _add(int a, int b)
{
return a + b;
}
[DllExport]
public static bool saySomething()
{
DialogResult dlgres = MessageBox.Show(
"Hello from managed environment !",
".NET clr",
MessageBoxButtons.OKCancel
);
return dlgres == DialogResult.OK;
}
C++ code (which calls previous C# code):
typedef int(__cdecl *_add)(int a, int b);
typedef bool(__cdecl *saySomething)();
auto pAdd = (_add)GetProcAddress(lib, "_add");
int c = pAdd(5, 7);
auto pSaySomething = (saySomething)GetProcAddress(lib, "saySomething");
bool dlgres = pSaySomething();
And a YouTube video with a demo at Managed & Unmanaged; PInvoke; [ Conari vs DllExport]. To be honest, the documentation is a cut below perfect, but don't let that put you off: the YouTube videos are excellent.
This project is inspired by another project from Robert Giesecke which has 220,000 downloads on NuGet.
Fun fact: some Python libraries have used this to implement functionality in a mix of C++ and C#.
And finally, thank you Robert Giesecke and Denis Kuzmin, brilliant, brilliant work!
If you don't care if your C++ program (or a portion of it) gets compiled with the /clr, you can use C++/CLI to simply call any .NET code (as long as you add a reference to it).
Try out this article.
Here is a nice tutorial.
The other route is to make your C# code be exposed as COM.
The easiest way is to use COM interop.
You could use a COM callable wrapper around your C# code compiled into a DLL.
From Microsoft: Write a custom .NET Core host to control the .NET runtime from your native code.
IOW: Call C# from from C++ on both Windows and Linux.
There is sample code on GitHub.
This sample code is cross platform, it allows C# code in .NET Core to be called from any C++ application on both Linux and Windows.
In all honesty, this solution seems to be quite complicated compared to the other DllExport answer. The C++ code is doing a lot of heavy lifting to scan for resouces and entry points, etc. One argument for this answer could be that it is cross-platform. However, the other DllExport answer is also cross-platform as well, and a lot simpler to use.
As an alternate approach, you could use Lua to instantiate the CLR objects, execute, and return the results.
I am trying to call a function at a specified memory address in c#, here is how I would go about it in C:
typedef void _do(int i);
auto doActor = (_do*)0xAAAABEEF;
doActor(1);
How do I replicate this behavior in C# if at all possible? Very new to C# all help is appreciated.
More in depth explanation of my situation: I am trying to create a tool that helps me automate certain processes within an executable. I decompiled the assembly of the main API and added my functionality (for the most part) by intercepting network packets/spoofing my own. I do not have control over the client side of things, stored in an obfuscated assembly that I can't de-/recompile. I seldomly need to call one or two functions out of this obfuscated assembly and I found the memory addresses of those relevant functions using a debugger but don't know where to go from here in c#.
The closest equivalent to a C function pointer in C# is a delegate. Delegates are managed, but you can convert one from the other with the Marshal.GetDelegateForFunctionPointer method:
public delegate void _do(int i); // the delegate type
var ptr = new IntPtr(0xAAAABEEF);
var doActor = Marshal.GetDelegateForFunctionPointer<_do>(ptr);
doActor(1);
There are limitations tied to this API, however. I suggest you take a look at the documentation.
If you're stuck with a version of .NET older than 4.5, you're going to have to use a different version of GetDelegateForFunctionPointer:
var doActor = (_do)Marshal.GetDelegateForFunctionPointer(ptr, typeof(_do));
I am writing code to parse a complicated string in C++ and create a tree from it. I would like to use C# in Visual Studio 2017 to call a native c++ method that returns a vector of nodes.
A Node looks like:
class node
{
public:
std::vector<node> subnodes;
std::string name;
};
and the c++ function might look like:
class noderizer
{
public:
node getNodes(std::string str);
};
what is the most efficient (coding time with secondary consideration for speed) way to call the noderizer::getNodes(...) member and create a equivalent class for c#?
I am assuming that the best route is to create a duplicate class definition in c# and then copy marshal the native std::strings into managed Strings"
public class node
{
public string name = string.Empty;
List<node> integers = new List<node>();
}
It's not clear if this article contains the latest information for c++ interop, but a related article on wrapping c++ native classes for use in c# indicates that I could most likely just wrap noderizer native c++ as noderizer * m_Impl; and then call the getNodes member and copy over each parameter. Is this the correct methodology?
You could use pInvoke as per your first referenced article, but the objects you are returning seem quite complicated. I think you will have a heck of a time with data marshalling if you're not already well versed (and even then). pInvoke is great for simple calls to C libraries where data marshalling is basic, but it gets very complicated very fast. This is not good for your situation.
The second article is closer to where you want to look. That being said, you have to consider whether you want to be wrapping a managed class or just calling a function that takes a string and returns your tree in managed format (i.e. it makes a copy rather than wrap unmanaged data). By your post it seems like you just need the latter.
Your best option is to use C++/CLI. Check out this tutorial. I am confident that taking this approach will make light work of your task. I won't attempt to explain the subject as the article above does a very good job. In essence, you will be able write functions with both managed and unmanaged data types, where all the data marshalling is built into the environment. A simple cast will marshal the data for you behind the scenes. As a big bonus, debugging is great as you can step from C# to C++/CLI to C++ code and back.
In the article above, the author does describe how to wrap an unmanaged class, which you can well do, but your problem will still be with data conversion.
I would approach your problem in 4 steps:
Write a static function getNodes() in C++/CLI that you can call from C# as any regular static method, passing a string as an argument. The article above will help you with that. Also See Here when creating the C++/CLI project.
getNodes() will use your C++ code to create a tree in its unmanaged form.
Use getNodes() to convert the tree from unmanaged to managed form.
Return the result to the caller in C#.
your declaration will look something like this, where the Node is your managed calss, ref keyword signifies that the class is managed, and ^ is the managed version of *.
public ref class noderizer
{
public:
static Node^ getNodes(String ^mStr);
};
Here getNodes() calls your C++ function and does the data conversion. I don't think it will take you long to figure it out.
Once you get a hang of the syntax, I think you will find it quite intuitive to use if you are already familiar with C# and C++.
As for performance, unless you're making thousands of consecutive calls or need critical real time data, it should not be an issue. One thing I would say though, if you're concerned with performance, you should write the pure C++ code in a separate purely unmanaged dll. I can't find the article for the life of me, but I remember looking at some benchmarks of executing purely unmanaged long running code block that was compiled inside the C++/CLI dll vs calling the exact same code that was compiled inside its own purely unmanaged dll. If I recall correctly, the separate dll was something like 3x faster.
I am working on creating a C++/CLI wrapper so that I can access a C# library in native C++. I've got about 60% of the wrapper finished, but I'm hitting a snag. The SDK for the C# library gives the method inputs/outputs as:
public bool GetNumBytesReceived(ref ulong numBytesReceived)
I'm at a loss as to how to grab numBytesReceived and pass it on to native C++. I feel like this question must have been asked before on SO, but I'm only seeing things that try to go the other way (from native C++ to C#). I've gotten the following to compile for my C++/CLI wrapper, but it gives a NullReferenceException when I access it from native C++:
public: bool NumBytesReceived(unsigned long long& numBytesReceived) {
return _CSManagedClass->GetNumBytesReceived(numBytesReceived);
}
I've also also been able to get it to compile without the input reference (&). Based on my debugging, the issue appears to be in the C++/CLI wrapper, I just don't know where.
Any help is appreciated, and I apologize if this has been asked already. I am still relatively green in the C family of languages.
I have a C source code written in VC++6.0 and I need that code to be used in a C# application which I am coding.
I have done few things to make that happen, I have run that C source file in release mode and have generated the intermediate.manifest file and the other files there, can I use any of these file to make my problem solved.
What you want to do is import the dll like this:
[DllImport("user32.dll")]//This is where you identify your dll...
public static extern int MessageBoxA( //This would be an object from your dll
int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, "Hello World!", "My Message Box", 0);
}
The keywords that you need to search on to learn about this are "running unmanaged code" and "PInvoke".
Another alternative is to wrap the C code in managed C++. Microsoft calls it C++/CLI. Anyways, you then compile an 'assembly' from that wrapper. An assembly is just a DLL that contains managed code. Then you can 'reference' (the managed equivalent of linking) that 'wrapper' from a fully managed C# application.
So the dependency could look like this:
C -> Managed C++ -> C#
If you are comfortable enough wrapping up c code in c++ you could easily make a dll by following this microsoft guide. It details how to go about creating a dll in C++. If you need a more in-depth explanation though feel free to get back to me, and I will try and knock up a quick how-to.
Also let me know if you use a different IDE or environment and I can taylor the answer to suit your needs more precisely.
Might be later on today though as am pressed for time at the moment.