C / C++ / MFC

//CCalibrationDialog.h
#pragma once
#include "afxcmn.h"
// CCalibrationDialog dialog
class CCalibrationDialog : public CDialog
{
	DECLARE_DYNAMIC(CCalibrationDialog)

public:
	CCalibrationDialog(CWnd* pParent = NULL);   // standard constructor
	virtual ~CCalibrationDialog();

// Dialog Data
	enum { IDD = IDD_DIALOG_CALIBRATION };
	CProgressCtrl m_ProgressCtrl;
.
.
.
protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
	virtual BOOL OnInitDialog();
	DECLARE_MESSAGE_MAP()
public:
	afx_msg void OnBnClickedButtonCalPrg();
};
//CCalibrationDialog.cpp
void CCalibrationDialog::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	DDX_Control(pDX, IDC_PROGRESS_CAL, m_ProgressCtrl);
}

BOOL CCalibrationDialog::OnInitDialog()
{
        m_ProgressCtrl.SetRange(0,100);
	m_ProgressCtrl.SetStep(10);
	return true;
}
.
.
.
void CCalibrationDialog::OnBnClickedButtonCalPrg()
{
	m_ProgressCtrl.StepIt();
}

CString result="";
CString str="test";

	const std::string s = str;//here gives an error

/*
error C2440: 'initializing' : cannot convert from 'CString' to 'std::basic_string<_Elem,_Traits,_Ax>'
*/

	std::string s1 = fun1(s);

	result=s1.c_str();