จะออก Report เป็น Excel แต่มัน Error ตรงสร้างตัวแปร WorkBook เกิดจากอะไรครับ ใช้ Visual Studio 2010

Imports System.Data
Imports System.Data.SqlClient
Imports Microsoft.Office.Interop.Excel.XlMSApplication
Imports System.IO

 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        con.Open()

        Dim sqlst As String = "select * from Types"
        Dim da As New SqlDataAdapter(sqlst, con)
        Dim ds As New DataSet
        da.Fill(ds, "type")

        'Export to Excel
        Dim filename As String = "MyXls/MyExcel.xls"

        'create excel
        Dim xlapp As New Microsoft.Office.Interop.Excel.Application
        Dim xlsheet1 As New Microsoft.Office.Interop.Excel.Worksheet
        Dim xlbook As New Microsoft.Office.Interop.Excel.Workbook
        Dim i As Integer
        Dim introw As Integer

        xlbook = xlapp.Workbooks.Add()
        xlbook.Application.Visible = False

        'create sheet1
        xlsheet1 = xlbook.Worksheets(1)
        xlsheet1.Name = "My Sheet1"

        'width & hight (A1:A1)

        xlapp.ActiveSheet.range("A1:A1")
        xlapp.ColumnWidth = 10.0

        xlapp.ActiveSheet.range("B1:B1")
        xlapp.ColumnWidth = 13.0

        xlapp.ActiveSheet.range("C1:C1")
        xlapp.ColumnsWidth = 23.0

        xlapp.ActiveSheet.range("D1:D1")
        xlapp.ColumnsWidth = 12.0

        xlapp.ActiveSheet.range("E1:E1")
        xlapp.ColumnsWidth = 13.0

        xlapp.ActiveSheet.range("F1:F1")
        xlapp.ColumnsWidth = 12.0

        xlapp.ActiveSheet.range("A1:F1")
        xlapp.BORDERS.Weight = 1
        xlapp.MergeCells = True
        xlapp.Font.Bold = True
        xlapp.Font.Size = 20
        xlapp.HorizontalAlignment = -4108

        xlapp.ActiveSheet.Cells(1, 1)
        xlapp.Values = "Type Report"

        'Header
        With xlapp.ActiveSheet.Cells(2, 1)
            .Value = "รหัส"
            .Font.Bold = True
            .VerticalAlignment = -4108
            .HorizontalAlignment = -4108
            .BORDER.Weight = 1
        End With

        With xlapp.ActiveSheet.Cells(2, 2)
            .Value = "ประเภท"
            .Font.Bold = True
            .VerticalAlignment = -4108
            .HorizontalAlignment = -4108
            .BORDER.Weight = 1
        End With

        ''''''''''''
        introw = 3
        For i = 0 To ds.Tables("type").Rows.Count - 1
            'detail
            With xlapp.ActiveSheet.Cells(introw, 1)
                .value = ds.Tables("type").Rows(i)
                .BORDER.Weight = 1
                .HorizontalAlignment = -4108
            End With

            With xlapp.ActiveSheet.Cells(introw, 2)
                .value = ds.Tables("type").Rows(i)
                .BORDER.Weight = 1
                .HorizontalAlignment = -4108
            End With
        Next
        Dim MyFile As New FileInfo(filename)

        If MyFile.Exists Then

            MyFile.Delete()

        End If

        MyFile = Nothing

        '*** Save Excel ***'
        'xlSheet1.PrintOut 1 '*** Print to printer ***'
        xlsheet1.SaveAs(filename)
        xlapp.Quit()

        '*** Quit and Clear Object ***'
        xlapp = Nothing
        xlsheet1 = Nothing
        xlbook = Nothing

        con.Close()
    End Sub