VB.NET สอบถามเกี่ยวกับ DataReader ในกรณีที่มีการ Read 2 ครั้ง

    Dim myDr As MySqlDataReader
    Dim myDrEr As MySqlDataReader
    Dim erRow As Integer = 0
        If objConn.State = ConnectionState.Open Then
            objConn.Close()
        End If
        Try
            objConn.ConnectionString = strConn
            objConn.Open()
        Catch
            MessageBox.Show("ไม่สารมารถติดต่อฐานข้อมูลได้กรุณาติดต่อผู้ดูแลระบบ")
            End
        End Try

        strSQL = "select hn from opddata where dep1 = '021'  AND left(icd10,1)<>'Z' and rdate between ('" & beginD & "') and ('" & endD & "') GROUP BY hn HAVING COUNT(hn) >1 order by hn "
        myCom = New MySqlCommand(strSQL, objConn)
        myDr = myCom.ExecuteReader
        
        While myDr.Read
            strSql1 = "select hn, rdate, name, icd10, icdName1 from opddata " & _
            " where hn = '" & myDr("hn") & "' and dep1 = '021'  AND left(icd10,1)<>'Z' and rdate between ('" & beginD & "') and ('" & endD & "')"
            myCom = New MySqlCommand(strSql1, objConn)
            myDrEr = myCom.ExecuteReader

            While myDrEr.Read
                DataGridView3.Rows.Add()
                DataGridView3.Item(0, erRow).Value = myDrEr("hn")
                DataGridView3.Item(1, erRow).Value = myDrEr("rdate")
                DataGridView3.Item(2, erRow).Value = myDrEr("name")
                DataGridView3.Item(3, erRow).Value = myDrEr("icd10")
                DataGridView3.Item(4, erRow).Value = myDrEr("icdName1")
                erRow += 1
            End While

            myDrEr.Close()

        End While

        myDr.Close()