How can one call/consume a .NET Assembly from a native binary?

[brimonk]

Put simply, I would like to attempt to call some C# code from an existing C/C++ codebase. In my experience in the past, I have generally found this to be hard, calling into a managed runtime from an unmanaged runtime, but I expected it might be possible as it seemed that dotnet compiled down into a .dll/.so of some sort, and was just called from a loading program.

Just for the record, I am trying to do this on Ubuntu 19.04.

So, I created a simple classlib by using, dotnet classlib. I filled out an example class within the given namespace that looked something like this: public class Foo { public int Add(int a, int b) { return a + b; } }. Then I attempted to use dotnet publish to get something that would be close to a Unix shared object (.so), and to my surprise, there wasn't one.

All I got was a .dll.

According to the documentation for the command, you can supposedly use the -r flag to set the runtime. So, I tried thelinux-x64, osx-x64 and win-x64 and only got PE32+ .dll's.

What's going on? Is it impossible to "just get a binary" from the dotnet core compiler? I know that C# compiles to an intermediate representation from within that .dll, but is there a way to skip that step, and compile a shared C# library into a "regular" library?

[Dotnet-GitSync-Bot]

I couldn't figure out the best area label to add to this issue. Please help me learn by adding exactly one area label.

[jkotas]

There is no straightforward way to publish .NET library as unmanaged library with C/C++ entrypoints today.

The closest thing that works today is hosting the runtime. The documentation is at
https://docs.microsoft.com/dotnet/core/tutorials/netcore-hosting

[AaronRobinsonMSFT]

@brimonk I have been working on a project for exposing C exports for a .NET assembly. It doesn't yet create a single binary for distribution, but it is a start. I mentioned it at #3750 (comment).

[AaronRobinsonMSFT]

As mentioned, the prototype project DNNE demonstrates an example of what is suggested in #34571 (comment).