求高手看一下此代码 “ Dim conn As ADODB.Connection” 用户定义类型未定义

Option Compare Database
Dim conn As ADODB.Connection
Dim rs As ADODB.Recordset
Private Sub Cmd_登录_Click()
   Set conn = CurrentProject.Connection
   Set rs = New ADODB.Recordset
   rs.Open "用户表", conn
   
   
   Dim username As String
   Dim userpass As String
   
   txt_用户名 .SetFocus
   username = txt_用户名.Text
   If IsNull(username) Or IsNull(txt_密码.Value) Then '判断用户名和密码是否为空
      MsgBox "用户名或密码不能为空，请重新输入!", vbOKOnly + vbInformation, "错误信息"
   Else
      If username <> rs!用户名 Then '判断用户名和密码是否正确
      MsgBox "用户名或密码不正确,请重新输入", vbOKOnly + vbInformation, "错误信息"
      txt_用户名.SetFocus
      txt_用户名.Text = ""
      txt_密码.SetFocus
      txt_密码.Value = ""
      txt_用户名.SetFocus
   Else
      '将登录时间计入数据库
      rs.Close
      rs.Open "用户登录记录表", conn, adOpenDYnamic, adLockOptimistic
      rs.AddNew
      rs!用户名 = username
      rs!登录时间 = Now()
      rs!退出时间 = CDate(0)
      rs.Update
      rs.Close
      DoCmd.Close
      DoCmd.OpenForm "质量管理系统窗体 "
      DoCmd.OpenForm "快捷面板"
   End If
End If
 End Sub


Private Sub Form_Load()
      txt_用户名.SetFocus '初始化窗口内容
      txt_用户名.Text = ""
      txt_密码.SetFocus
      txt_密码.Text = ""
      txt_用户名.SetFocus


End Sub