Question

I’ve one header file which is just methods, a second C++ file where those methods are implemented, and a third main file where I want to call a method from second C++ file.

I have shown on which lines the errors occur with comments.

Root.h file (just methods):

class Root
{
    //File
    public: void NewFile(void);
    public: void OpenFile(void);
    public: void SaveFile(void);
    public: void SaveAsFile(void);
    public: void Print(void);
    public: void Exit(void);

    //Edit
    public: void Undo(void);
    public: void Redo(void);
    public: void Cut(void);
    public: void Copy(void);
    public: void Paste(void);
    public: void SelectAll(void);

    //Tools
    public: void Options(void);

    //Help
    public: void About(void);
};

Root.cpp

#include "stdafx.h"
#include "Root.h"

using namespace System::Windows::Forms;
using namespace System::IO;

class Nroot : public Root
{
    void OpenFile()
    {
        OpenFileDialog^ opf = gcnew OpenFileDialog();
        opf->InitialDirectory = "C://";
        opf->Filter = "Text Files|*.txt";
        if(opf->ShowDialog() == DialogResult::OK) //here is first error C3063: operator '==':  all operands must have the same enumeration type 
        {
            StreamReader^ sr = gcnew StreamReader(opf->FileName);
            MessageBox::Show(sr->ReadToEnd());
        }
    }
};

Main File (just event)

private: System::Void openToolStripMenuItem_Click(System::Object^  sender, System::EventArgs^  e) {
    Nroot nr;
    nr.OpenFile; //here is second error C3867: 'WindowsFormsApplication2::Nroot::OpenFile': function call missing argument list; use '&WindowsFormsApplication2::Nroot::OpenFile' to create a pointer to member c:\users\srdjan\documents\visual studio 2012\projects\windowsformsapplication2\windowsformsapplication2\Form1.h 325
}

Answer 1

1. Looks like DialogResult::OK enumeration value defined differently more then in one place, so you have to use full path to the value: ::System::Windows::Forms::DialogResult::OK. At least MSDn example does so:

   if(opf->ShowDialog() == ::System::Windows::Forms::DialogResult::OK)
   

2. You’ve forgotten parenthesis:

   nr.OpenFile();
              ^^
   

3. To access Nroot::OpenFile() outside of the class, you should make it public. In c++, private access modifier is applied to members by default:

   class Nroot : public Root
   {
   public:
       void OpenFile()
   //...