///////////////////////////////////////////////////////////////////////////
// cs_callback is used to marshall callbacks. It allows a C# function to
// be passed to C++ as a function pointer through P/Invoke, which has the
// ability to make unmanaged-to-managed thunks. It does NOT allow you to
// pass C++ function pointers to C#.
//
// Anyway, to use this macro you need to declare the function pointer type
// TYPE in the appropriate header file (including the calling convention),
// declare a delegate named after CSTYPE in your C# project, and use this
// macro in your .i file. Here is an example:
//
// in C++ header file (%include this header in your .i file):
// typedef void (__stdcall *Callback)(PCWSTR);
// void Foo(Callback c);
//
// in C# code:
// public delegate void CppCallback([MarshalAs(UnmanagedType.LPWStr)]
//                                  string message);
//
// in your .i file:
// %cs_callback(Callback, CppCallback)
//
// As an alternative to specifying __stdcall on the C++ side, in the .NET
// Framework (but not the Compact Framework) you can use the following
// attribute on the C# delegate in order to get compatibility with the
// default calling convention of Visual C++ function pointers:
// [UnmanagedFunctionPointerAttribute(CallingConvention.Cdecl)]
//
// Remember to invoke %cs_callback BEFORE any code involving Callback.
%define %cs_callback(TYPE, CSTYPE)
        %typemap(ctype) TYPE, TYPE& "void*"
        %typemap(in) TYPE  %{ $1 = ($1_type)$input; %}
        %typemap(in) TYPE& %{ $1 = ($1_type)&$input; %}
        %typemap(imtype, out="IntPtr") TYPE, TYPE& "CSTYPE"
        %typemap(cstype, out="IntPtr") TYPE, TYPE& "CSTYPE"
        %typemap(csin) TYPE, TYPE& "$csinput"
%enddef

typedef void (__stdcall *Callback)(PCWSTR);
ApplicationIo(Callback c);     // ApplicationIo is just my class that will use the callback.

%module II_Interface_DLL

%{
#include "II_Interface_DLL.h" //This is the header file for my DLL
%}

//Other SWIG libs are included here

%define %cs_callback(TYPE, CSTYPE)
        %typemap(ctype) TYPE, TYPE& "void*"
        %typemap(in) TYPE  %{ $1 = ($1_type)$input; %}
        %typemap(in) TYPE& %{ $1 = ($1_type)&$input; %}
        %typemap(imtype, out="IntPtr") TYPE, TYPE& "CSTYPE"
        %typemap(cstype, out="IntPtr") TYPE, TYPE& "CSTYPE"
        %typemap(csin) TYPE, TYPE& "$csinput"
%enddef

%cs_callback(Callback, CppCallback)

%include "II_Interface_DLL.h"

public delegate void CppCallback([MarshalAs(UnmanagedType.LPWStr)] string newText);
public void UpdateLog(string newText) { //stuff }   // The function I want to pass as the callback
CppCallback logCallback = new CppCallback(this.UpdateLog);
ApplicationIo IO = new ApplicationIo(logCallback); //This is the line where the error gets flagged