problem with const string&

Hello,

I am new to visual C++ and can anyone please kindly help me out this
problem

I had a problem using const string& here is the sample code

class Ctrial1Dlg : public CDialog
{
// Construction
public:
    Ctrial1Dlg(CWnd* pParent = NULL); // standard constructor
    void getdata();
// Dialog Data
    enum { IDD = IDD_TRIAL4_DIALOG };

    protected:
    virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support

// Implementation
protected:
    HICON m_hIcon;

    // Generated message map functions
    virtual BOOL OnInitDialog();
    afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
    afx_msg void OnPaint();
    afx_msg HCURSOR OnQueryDragIcon();
    DECLARE_MESSAGE_MAP()
public:
    afx_msg void OnBnClickedExit();
public:
    afx_msg void OnBnClickedCapture();
public:
    Device* getDeviceFromUserInput(const DeviceManager& devMgr);
public:
    afx_msg void OnBnClickedSave();
public:
    int SaveImage(const string &filename);

};

when I had defined SaveImage and passing const string& filename I am
getting two errors

1. error C4430: missing type specifier -int assumed (However I had
used int)

2. error C2143: missing ',' before '&'

Thanks in advance,
Raj.