How to highlight text inside a CEdit field inside OnInitDialog

I'm able to display a few characters inside a CEdit control by using the code shown below in the OnInitDialog() function, but I'm not able to highlight the same text within the body of the OnInitDialog() function. I just don't know how to do it. In my CReplaceCharacterDlg class I added using the wizard a CEdit ReplaceCharsCtrl variable and created the CEdit control using the resource editor. I tried the following line in my OnInitDialog() function as seen below but get a Debug Assertion Failed error. Can someone give me a hint on this can be done please ?

// CReplaceCharacter dialog

class CReplaceCharacterDlg : public CDialogEx
{
    DECLARE_DYNAMIC(CReplaceCharacterDlg)

public:
    CReplaceCharacterDlg(CWnd* pParent = nullptr);   // standard constructor
    CReplaceCharacterDlg(CWnd* pPar, CStringW replaceStrW);
    virtual ~CReplaceCharacterDlg();

// Dialog Data
#ifdef AFX_DESIGN_TIME
    enum { IDD = IDD_REPLACE_CHAR };
#endif

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

    DECLARE_MESSAGE_MAP()
public:
    CEdit ReplaceCharsCtrl;
    CStringW ReplacementCharacterStr;
    afx_msg void OnBnClickedOk();
};

// Implementation
BOOL CReplaceCharacterDlg::OnInitDialog()
{
    GetDlgItem(IDC_EDIT1)->SetWindowTextW(ReplacementCharacterStr);
        ReplaceCharsCtrl.SetHighlight(0, 2);  <---- GIVES ASSERT ERROR  ReplaceCharsCtrl hWnd = NULL
    return TRUE;
}

See the body of the post.

Change your code as shown below (partially based on @Mark Ransom comments):

BOOL CReplaceCharacterDlg::OnInitDialog()
{
    CDialogEx::OnInitDialog(); // Do not delete this, among others binds control variables to controls
    ReplaceCharsCtrl.SetWindowTextW(ReplacementCharacterStr); // Control is already bound to IDC_EDIT1, no need do create a temporary CWnd object
    ReplaceCharsCtrl.SetSel(0, -1); // Select the entire text
    ReplaceCharsCtrl.SetFocus();
    return FALSE; // We explicitly set the focus to a non-default control

}

EDIT:

Finally made some test and found that the SetHighlight() function (EM_SETHILITE message) has no effect, it is a relic of some very old versions of Windows. It does nothing and the Win32 documentation says it is "not implemented". Also found this post. You can use SetSel() instead, as you have already found.