DataGridのデータをexcelのcsv形式で出力したい

Dim colToList As System.Web.UI.WebControls.DataGridColumn
'LOOP FOR DataGridColumns　方向イメージ→
For Each colToList In dgHYOKA.Columns 
　strRow = "" 
　If strRow <> "" Then 
　　strRow = strRow & "," 
　End If
　'ヘッダーテキスト
　strRow = strRow & colToList.HeaderText
　Response.Write(strRow & vbNewLine) 
Next colToList

Dim rowToList As System.Web.UI.WebControls.DataGridItem 
Dim cellToList As System.Web.UI.WebControls.TableCell 
'LOOP FOR DataGridItem　方向イメージ↓
For Each rowToList In dgHYOKA.Items 
　strRow = ""
　'LOOP FOR TableCell　方向イメージ→
　For Each cellToList In rowToList.Cells 
　　If strRow <> "" Then
　　　strRow = strRow & "," 
　　End If 
　　strRow = strRow & cellToList.Text 
　Next cellToList 
　Response.Write(strRow & vbNewLine) 
Next rowToList

   Private Sub dgHYOKA_ItemDataBound(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs) Handles dgHYOKA.ItemDataBound

        Dim i As Integer
        Select Case e.Item.ItemType
            Case ListItemType.Header                                'ヘッダー

                'HeaderText設定（←Postback時消えてしまう）
                'For i = 0 To e.Item.Cells.Count - 1
                '    Dim AddColumn As New BoundColumn()
                '    AddColumn.HeaderText = e.Item.Cells(i).Text
                '    dgHYOKA.Columns.AddAt(i, AddColumn)
                'Next i

                'csv出力用文字列作成
                Dim strToExlTitle As String = ""
                For i = 0 To e.Item.Cells.Count - 1
                    If strToExlTitle <> "" Then
                        strToExlTitle &= ","
                    End If
                    strToExlTitle &= e.Item.Cells(i).Text
                Next i
                ViewState("ToExlTitle") = strToExlTitle
        End Select

    End Sub

    Private Sub btnExp_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExp.Click

        Dim strFilename As String = "test"

        Response.Clear()
        Response.ContentEncoding = System.Text.Encoding.GetEncoding("shift-jis")
        Response.ContentType = "application/vnd.ms-excel"
        Response.AppendHeader("Content-Disposition", "attachment; filename=" & strFilename & ".csv")

        Dim headerToList As System.Web.UI.WebControls.TableHeaderCell
        Dim rowToList As System.Web.UI.WebControls.DataGridItem
        Dim cellToList As System.Web.UI.WebControls.TableCell

        'ﾀｲﾄﾙ
        Response.Write(CType(ViewState("ToExlTitle"), String) & vbNewLine)

        'ﾃﾞｰﾀ
        For Each rowToList In dgHYOKA.Items
            Dim strRow As New System.Text.StringBuilder()
            For Each cellToList In rowToList.Cells
                If strRow.Length <> 0 Then
                    strRow.Append(",")
                End If
                If cellToList.Text = " " Then
                    cellToList.Text = ""
                End If
                strRow.Append(cellToList.Text)
            Next cellToList
            Response.Write(strRow.ToString & vbNewLine)
        Next rowToList

        Response.End()