The ConnectionString property has not been initialized. ช่วยทีคับ

 Public Sub ReadConfig()
       strConn = "Data Source=PTK530080085-PC\sqlexpress;Initial Catalog=TestProject;Integrated Security=True;Pooling=False"
    End Sub

อันนี้ไว้เปิดคับ 
 ReadConfig()
        With conn
            If .State = ConnectionState.Open Then .Close()
            .ConnectionString = strConn
            .Open()
        End With

 With cmds
          conn.Open()  

          .CommandType = CommandType.Text
          .CommandText = sqlC
          .Connection = conn

          dd = .ExecuteReader()

          While dd.Read()

              ComboBox_M_Region.Items.Add(dd.GetString(0))

          End While
      End With

With conn
            If .State = ConnectionState.Open Then .Close()
            .ConnectionString = strConn
            .Open()
        End With

Public Function conn() As System.Data.OleDb.OleDbConnection
        Dim cnn As New System.Data.OleDb.OleDbConnection
        cnn.ConnectionString = "Data Source=PTK530080085-PC\sqlexpress;Initial Catalog=TestProject;Integrated Security=True;Pooling=False"
        cnn.Open()
        Return cnn
    End Function

Public Sub ComboboxRegionReload()
      Dim cmds As New SqlCommand

      Dim sqlC As String = ""
      Dim dd As SqlDataReader
      sqlC = "select Region_manager_name from P_D_Region_Manager"
      ComboBox_M_Region.Text = ""
      ComboBox_M_Region.Items.Clear()
      With cmds
          .CommandType = CommandType.Text
          .CommandText = sqlC
          .Connection = conn
          dd = .ExecuteReader()
          While dd.Read()
              ComboBox_M_Region.Items.Add(dd.GetString(0))
          End While
      End With
      dd.Close()
      ComboBox_M_Region.Text = "กรุณาเลือกข้อมูล" 'ใส่ตอน เรียกข้อมูลใส่ cobo เสร็จแล้ว
      conn.Close()
  End Sub