Dotnet interop playground

Playground to test interop between managed and unmanaged code using .NET.

How .NET (managed) can call native libraries

From the cross-platform perspective, the solution is P/Invoke. With few lines of code, a C# code can call a function from a native library loaded with DllImport.

The important point using DllImport is to place the dll/so files correctly. The DllImport path is relative to the main program executing, and not the C# dll! (need to be tried but perhaps absolute paths works well... but deploying an app is never done with absolute path as the distant machine configuration is not known in advance). Build systems are here to copy files where they have to be before being deployed.

How native code (unmanaged) can call .NET (managed) functions.

Here, there is two ways:

1. Embedding the .NET runtime into a native application, and the runtime is instanciated by this application which then can execute any managed dll (IL). This required a bit of setup adding the required headers for the native application to compile, and the runtime must be accessible to actually run the dll.
2. Using the recent NativeAOT feature, which compiles the IL directly to native code. Very easy, only one NuGet package to import into the .NET project and a publish. And the runtime is no longer required.

In both cases, there are some limitations, and the most important ones are: * Functions in C# must be static. * Limited to primitive types (and see marshalling).

In this project, both implementations are done for experimental purposes.

Goals

The goals here are: * Understand how interop works * Test Marshalling to know how data can be passed back and forth

Repo hierarchy

• managed-pinvoke: C# code calls C++ library with P/Invoke (explicit).
• native-aot: C program calls C# from a native assembly compiled from C# with NativeAOT.
• native-host: C++ program calls C# from a hosted runtime using hostfxr.

Compilation

Each project that requires compilation has a build.bat and build.sh file. No other tool is used in order to keep things very simple. In a real world project, MsBuild using csproj, Scons or [c]Make are usually used. Each project contains a README.md to contextualize more specifically is needed.

Disclaimer

This project is very exploratory and experimental. So any advices or remarks are very welcomed!