Calling C# code from C++
C#C++ CliInteropC# Problem Overview
I need to be able to invoke arbitrary C# functions from C++. http://www.infoq.com/articles/in-process-java-net-integration 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?
C# Solutions
Solution 1 - C#
There are several ways for a C++ application to invoke functions in a C# DLL.
- Using C++/CLI as an intermediate DLL
- Reverse P/Invoke
- Using COM
- 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)
- https://stackoverflow.com/q/19999049/184528
- 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)
Solution 2 - C#
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++ ...
Solution 3 - 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!
Solution 4 - C#
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.
EDIT: Here is a nice tutorial
The other route is to make your C# code be exposed as COM.
Solution 5 - C#
The easiest way is to use COM interop.
Solution 6 - C#
You could use a COM callable wrapper around your C# code compiled into a DLL.
Solution 7 - C#
As an alternate approach, you could use Lua to instantiate the CLR objects, execute, and return the results.
Solution 8 - C#
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.