发送HTTP标头后，服务器无法附加标头。 vb.net

Question

我正在处理我应该将信息导出到csv文件的内容，但是当我尝试在行Response.AddHeader(" content-disposition "attachment; filename = GridViewExport.csv")

中下载它时

我收到错误：

  

在发送HTTP标头后，服务器无法追加标头。

我的gridview位于og更新面板

内

Public Sub archivoGenerado()

    For Each RW As GridViewRow In Dgdatoo.Rows
        If CType(RW.Cells(10).FindControl("CheckBox2"), CheckBox).Checked = True Then
            'If CType(RW.Cells(10).FindControl("Radio"), RadioButton).Checked = True Then
            Dim estatus As [String] = CType(RW.Cells(8).FindControl("LabEs"), Label).Text
            Dim Centro As [String] = DirectCast(RW.Cells(1).FindControl("LabeCe"), Label).Text
            Dim almacen As [String] = DirectCast(RW.Cells(3).FindControl("LabeAl"), Label).Text
            Dim Dupla As [String] = DirectCast(RW.Cells(6).FindControl("LabeDu"), Label).Text

            Dim constr As New Data.SqlClient.SqlConnection
            constr.ConnectionString = C.GetAppConfiguracion("Inventario", "ConnInventario")
            Using cmd As New SqlCommand("Select Vw_RptInventarioSAP.IdMaterial as 'Barcode / Item-ID',Vw_RptInventarioSAP.MaterialNombre as'Description',S_AsignacionDuplas.Cantidad as 'Quantity',Vw_RptInventarioSAP.IdLote as 'Lote',S_AsignacionDuplas.IdCentro as 'Centro',S_AsignacionDuplas.IdAlamacen as 'Almacen',S_AsignacionDuplas.IdDupla as 'Dupla' from Vw_RptInventarioSAP inner join S_AsignacionDuplas on Vw_RptInventarioSAP.IdMaterial = S_AsignacionDuplas.IdMaterial where S_AsignacionDuplas.IdDupla = '" & Dupla & "' and IdCentro ='" & Centro & "' and IdAlmacen= '" & almacen & "'")
                Using sda As New SqlDataAdapter()
                    cmd.Connection = constr
                    sda.SelectCommand = cmd
                    Dim da As New SqlDataAdapter(cmd)
                    Using dt As New DataTable()
                        sda.Fill(dt)

                        'Build the CSV file data as a Comma separated string.
                        Dim csv As New StringBuilder()
                        For i As Integer = 0 To dt.Columns.Count - 1
                            csv.Append(dt.Columns(i).ColumnName + ",")
                        Next

                        csv.Append(Environment.NewLine)

                        For j As Integer = 0 To dt.Rows.Count - 1
                            For k As Integer = 0 To dt.Columns.Count - 1
                                csv.Append(dt.Rows(j)(k).ToString() + ",")

                            Next
                            csv.Append(Environment.NewLine)
                        Next
                        For Each RW2 As GridViewRow In Dgdatoo.Rows

                            Response.Clear()
                            Response.ClearContent()

                            Response.ContentType = "text/csv"
                            Response.AddHeader("content-disposition","attachment;filename=GridViewExport.csv")

                            Response.Write(csv.ToString())
                            Response.Flush()




                        Next


                        'Next

                    End Using
                End Using
            End Using
        Else
            With lbError0
                .Visible = True
                .Text = "Selecionar inventario a descargar"
            End With
        End If
    Next

End Sub