对话框元素显示为null

Question

void CMFCSterlingViewAppView::OnActionView()
{   
    CMFCSterlingViewAppDoc* doc = GetDocument();
    // TODO: Add your command handler code here
    if (indexEdit >= 0)
    {

    ViewDialog dlg;

    dlg.m_EditId;

    if (dlg.DoModal() == IDOK)
                {

                }
   }
}


void ViewDialog::DoDataExchange(CDataExchange* pDX)
{
    CDialog::DoDataExchange(pDX);
    DDX_CONTROL(pDX, IDC_STATIC28, m_EditId);
}

对话框m_EditId显示为null。为什么它是空的？