vbNullString [VBA]

option explicit 

public sub vb_null_string() 

  dim str_quotequote as string
  str_quotequote = ""

  dim strUninitialized as string

  if str_quotequote = vbNullString then
     msgBox("str_quotequote = vbEmptyString")       ' str_quotequote = vbEmptyString
  else
     msgBox("not str_quotequote = vbEmptyString")
  end if

  if str_quotequote <> vbNullString then
     msgBox("str_quotequote <> vbEmptyString")        
  else
     msgBox("not str_quotequote <> vbEmptyString")  ' not str_quotequote <> vbEmptyString
  end if

  '-

  if strUninitialized = vbNullString then
     msgBox("strUninitialized = vbEmptyString")       ' strUninitialized = vbEmptyString
  else
     msgBox("not strUninitialized = vbEmptyString")
  end if

  if strUninitialized <> vbNullString then
     msgBox("strUninitialized <> vbEmptyString")      
  else
     msgBox("not strUninitialized <> vbEmptyString")  ' not strUninitialized <> vbEmptyString
  end if

  '-

'   Type mismatch:
'   --------------
'
' if vbEmpty = vbNullString then
'    msgBox("vbEmpty = vbNullString")
' else 
'    msgBox("not vbEmpty = vbNullString")
' end if

end sub