This example shows how to create a simple function that adds two numbers together by creating a simple DLL in C++ with Visual Studio 2019 that can be used in Xojo 2019 r1.1. The secret is that the functions will need to have "C"-like names to prevent name mangling. This example is for 64-bit applications.

Raw Plugin Screen Grab

Here are the steps to create the plugin in Visual Studio 2019 and read the DLL in Xojo.

  • Start Visual Studio 2019
  • Create a new project
  • Select Dynamic-Link Library with exports (DLL)
  • Create project name RawPluginCPlusPlus code

Add code to RawPluginCPlusPlusCode.cpp

// RawPluginCPlusPlusCode.cpp : Defines the exported functions for the DLL.


#include "pch.h"

#include "framework.h"

#include "RawPluginCPlusPlusCode.h"

// This is an example of an exported function.



       return x + y;


Add code to RawPluginCPlusPlusCode.h

// The following ifdef block is the standard way of creating macros which make exporting

// from a DLL simpler. All files within this DLL are compiled with the RAWPLUGINCPLUSPLUSCODE_EXPORTS

// symbol defined on the command line. This symbol should not be defined on any project

// that uses this DLL. This way any other project whose source files include this file see

// RAWPLUGINCPLUSPLUSCODE_API functions as being imported from a DLL, whereas this DLL sees symbols

// defined with this macro as being exported.


#define RAWPLUGINCPLUSPLUSCODE_API __declspec(dllexport)


#define RAWPLUGINCPLUSPLUSCODE_API __declspec(dllimport)


extern "C" RAWPLUGINCPLUSPLUSCODE_API int AddTwo(int x, int y);

  • Select ‘Release’ and ‘x64’ configuration in Visual Studio
  • Select Build menu and press Build Solution
  • Start Xojo 2019 r1.1
  • Create a new Desktop project in Windows and save it as RawPlugin.xojo_binary_file
  • Change the Xojo project to an x64 application
  • Copy the dll file from C:\Users\Owner\Desktop\New\RawPlugin\RawPluginCPlusPlusCode\x64\Release\ RAWPLUGINCPLUSPLUSCODE.dll and paste it beside the RawPlugin.xojo_binary_file
  • Add three TextFields to hold two numbers from the user (numbers to be added) and the last Textfield to show the answer.
  • Add the following code to an action event

Sub Action() Handles Action

  Declare Function AddTwo Lib "C:\Users\Owner\Desktop\New\RawPlugin\RAWPLUGINCPLUSPLUSCODE.dll" (x as Integer, y as Integer) As Integer

  Dim Answer as Integer


  If System.IsFunctionAvailable("AddTwo", "C:\Users\Owner\Desktop\New\RawPlugin\RAWPLUGINCPLUSPLUSCODE.dll") Then

    Answer = AddTwo(5, 3) //Add 5 + 3

    Answer = AddTwo(TFFirstNumber.Text.CLong, TFSecondNumber.Text.CLong)


    Answer = 0 //Error

  End If


  TFAnswer.Text = Answer.ToText

End Sub


The code can be downloaded at Github Raw Plugin.

Thats it! This program was created in Visual Studio C++ 2019, and Xojo 2019 r1.1 on the 23rd of September 2019.