Use C# library from any^* language

This repo demonstrates how to use .NET 7's Native AOT feature to build a native DLL that can be called from other languages, such as Java and Python.

1. Enable native AOT publishing

In the .csproj file add <PublishAot>true</PublishAot> (see example)

2. Expose native functions

Associate the C# native functions with the [UnmanagedCallersOnly] attribute (see example)

3. Publish to a native DLL

For these examples the native DLL is published to /native-demo/native-c#.dll:

dotnet publish ./_native-c#/ -r win-x64 -o /native-demo

4. Use the native DLL in any^* language

Load the library at runtime and call the native functions. See examples in:

• C#
• C++
• F#
• Go
• Java
• JavaScript
• Kotlin
• Python
• Ruby
• Rust
• Visual Basic

All examples showcase using native functions that:

• prints a message to the console,
• returns a 32-bit integer (7 + 2, 7 - 2),
• returns a 64-bit double (7 * 2, 7 / 2),
• modifies an array of 64-bit doubles (array[i] = (i * 2) + 0.5)

The output should look something like:

Hello from native code written in C#!
9
5
14.0
3.5
[0.5, 2.5, 4.5, 6.5, 8.5]

* * *

Note

I spent a long time trying to get this to work in MATLAB and R but ultimately failed. Both languages seem to require some level of C wrapper to work. I would be very interested to see a solution to this!