Suitable IPC between a C++ DLL (local hooks) and C# application

Whats the best inter-process communication for a C++ DLL that's injected into a third-party process and a C# application? Here's the current situation:

// This gets executed within the target process memory region
LRESULT CALLBACK HookProc(int code, WPARAM wParam, LPARAM lParam)
{
    if (code > 0)
    {
        auto csharpApplicationFunctionPointerAddress = 0xdeadbeef;
        auto csharpApplicationFunctionResult = call csharp function with N parameters here

        // Do something with the result
        if (csharpApplicationFunctionResult == "foo")
        {
            
        }
    }

    return CallNextHookEx(hookInstance, code, wParam, lParam);
}

I've come across this and figured out I'd need a RPC, however I can't seem to find the best suitable RPC for this problem, as that communication requires passing N parameters and getting the result back as fast as possible.

NOTES:

1. Sockets are out of mind as I dont want to deal with timeouts
2. Would named pipes work here or it's only advisable for string messages?(serialization/deserialization is out of mind)
3. I do not want to use message polling with a remote thread, as this uses too much CPU

Are even there any options left? Feel free to correct me the notes above.