Failed to create a dll with constructors in the classes

Question

I created a header with dll settings:

globaldef. h

#pragma once

#ifdef OPENXML_LIB
#define OPENXML __declspec(dllexport)
#else
#define OPENXML __declspec(dllimport)
#endif // OPENXML_LIB

I have created two classes so far:

xmldoc. h

#pragma once

#define XML_MODE_R 0
#define XML_MODE_RW 1

#include "globaldef.h"
#include <fstream>
#include <string>

class OPENXML XmlDocumment {

public:

    XmlDocumment(std::string fileName, int mode);
    ~XmlDocumment();

    //Load xml content to string
    virtual std::string read();

private:

    //Xml file
    std::fstream xmlFile;
    std::string filename;
    int mode = 0;

};

xmldoc.cpp

#include "stdafx.h" 
#include "xmldoc.h" 
XmlDocumment::XmlDocumment(std::string fileName, int mode) { 
     this->filename = fileName; 
     this->mode = mode; 
} 
XmlDocumment::~XmlDocumment() { } 
std::string XmlDocumment::read() { 
     switch (mode) { 
         case XML_MODE_R: xmlFile.open(filename, std::ios::in); break; 
         case XML_MODE_RW: break; 
     } 
std::string content((std::istreambuf_iterator<char>(xmlFile)), (std::istreambuf_iterator<char>())); 
xmlFile.close(); 
return content; 

}

And the other class at the time I didn’t start writing

xmlnode. h

#pragma once

#include "globaldef.h"

class OPENXML XmlNode {

public:


};

Everything builds normally if there is no constructor, but if I add a constructor even without any parameters or empty, the compiler sends the following error: