Error การ upload excel to database คับช่วยดูให้หน่อย

Imports System.Data
Imports System.Data.OracleClient
Imports Excel

Partial Class ADD
    Inherits System.Web.UI.Page
    Dim Conn As OracleConnection
    Dim Cmd As OracleCommand
    Dim sqlx As String
    Dim dtReader As OracleDataReader

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        If Not IsNothing(myFile1.PostedFile) Then
            Dim UlFileName As String
            Dim I As Integer

            UlFileName = "Myfile/" & System.IO.Path.GetFileName(myFile1.Value)
            myFile1.PostedFile.SaveAs(Server.MapPath(UlFileName))

            Dim xlApp As New Excel.Application
            Dim xlBook As Excel.Workbook
            Dim xlSheet1 As Excel.Worksheet

            xlBook = xlApp.Workbooks.Open(Server.MapPath(UlFileName))
            xlBook.Application.Visible = False
            xlSheet1 = xlBook.Worksheets(1)

            Dim dt As New System.Data.DataTable
            Dim dr As System.Data.DataRow

            dt.Columns.Add("STUDENTCODE")
            dt.Columns.Add("STUACTIVITY_ID")
            I = 2

            Do While Not Trim(xlSheet1.Cells.Item(I, 1).value) = ""
                dr = dt.NewRow
                dr("STUDENTCODE") = xlSheet1.Cells.Item(I, 1).value
                dr("STUACTIVITY_ID") = xlSheet1.Cells.Item(I, 2).value
                dt.Rows.Add(dr)
                I = I + 1

            Loop

            For I = 0 To dt.Rows.Count - 1

                sqlx = "INSERT INTO DATAAPP.STU_EXCEL (ID,STUDENTCODE,STUACTIVITY_ID)"
                sqlx &= "VALUES(SQ_EXCEL.NEXTVAL,'" & dt.Rows(I)("STUDENTCODE") & "','" & dt.Rows(I)("STUACTIVITY_ID") & "')"
                'Response.Write(sql_add)
                Cmd = New OracleCommand(sqlx, Conn)
                Cmd.ExecuteReader()

            Next
            Me.lblText.Text = "บันทึกข้อมูลเรียบร้อย"
            xlApp.Application.Quit()
            xlApp.Quit()
            xlSheet1 = Nothing
            xlBook = Nothing
            xlApp = Nothing


        End If
    End Sub

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim strconnstring As String
        strconnstring = "Data Source=dataapp;User Id=dataapp;Password=xxxx;"
        Conn = New OracleConnection(strconnstring)
        Conn.Open()


    End Sub
End Class