What approach can I take to calling into a non c-style native c++ interface which from just the dll from .NET ?

Question

I've been browsing the web for over 48 hours reading up on interoperability and playing around with Pinvoke and C++/Cli (very limited the latter). There is an unmanaged c++ api (a namespace containing a lot of exported structs which contain methods, all pure virtual and implemented across several cpp files as classes and what not) and I would like to call into them from .NET. I do not really have access to the source code, only to the resulting dll and so It seems c++/cli would not work. But on the other hand, I have not been able to find examples, tutorials, or documentation of using Pinvoke for non c-style like apis which have namespace and structs and classes containing methods. I believe if they are exposed, the dll SHOULD contain entrypoints albeit mangled up in name...is my only choice without source code access then to do this? And if I may also ask..supposing i had access to the source code, what would be the most non-intrusive way (i.e. requiring the least modification if any) to wrap the api for .net use?

Thanks

Answer 1

If you have the header (or can make one from the documentation) you should be able to write a C++/CLI wrapper. It's just C++. Ideally there would also be a convenience lib, then you could just include the header link to the lib.

Your C++/CLI code would be simple wrappers around the unmanaged classes, something like:

public ref class Foo
{
  private:
     NativeFoo f;
  public:
    int method1(int i) {return f.method1(int i);}
// etc
};

[disclaimer: I'm typing code into the answer box. Possible typos I suppose.]

You build that, your C# code adds a reference to the resulting assembly, then in your C# code you just use Foo as the managed type that it is.

This is going to be a lot easier than figuring out mangled names. Yes?