How to export C# methods?

Question

How can we export C# methods?

I have a dll and I want to use its methods in the Python language with the ctypes module. Because I need to use the ctypes module, I need to export the C# methods for them to be visible in Python.

So, how can I export the C# methods (like they do in C++)?

Answer 1

(This may no longer be relevant since SLaks has found that ingenious link, but I'll leave an edited version for reference...)

The "normal" way of exposing .NET/C# objects to unmanaged code (like Python) is to create a COM-callable wrapper for the C# DLL (.NET assembly), and call that using Python's COM/OLE support. To create the COM-callable wrapper, use the tlbexp and/or regasm command-line utilities.

Obviously, however, this does not provide the C/DLL-style API that SLaks' link does.

Answer 2

Contrary to popular belief, this is possible.
See here.

Answer 3

That's not possible. If you need DLL exports you'll need to use the C++/CLI language. For example:

public ref class Class1 {
public:
  static int add(int a, int b) {
      return a + b;
  }
};

extern "C" __declspec(dllexport) 
int add(int a, int b) {
  return Class1::add(a, b);
}

The class can be written in C# as well. The C++/CLI compiler emits a special thunk for the export that ensures that the CLR is loaded and execution switches to managed mode. This is not exactly fast.

Writing [ComVisible(true)] code in C# is another possibility.

Answer 4

With the normal Python implementation ("CPython"), you can't, at least not directly.

You could write native C wrappers around our C# methods using C++/CLI, and call these wrappers from Python.

Or, you could try IronPython. This lets you run Python code and call code in any .Net language, including C#.