SitecoreAdminPageCsvExport_ExportButtonClick.aspx

/// <summary>
/// Gets executed by the ExportButton OnClick event
/// </summary>
protected void ExportButtonClick(object sender, EventArgs e)
{
    try
    {
        List<Item> childItemList = GetChildrenFromTargetItem(TargetTextBox.Text, SummaryLiteral);
        if (!childItemList.Any())
        {
            SummaryLiteral.Text = "No Child items for specified target item";
            return;
        }

        ExportButton.Enabled = false;
        Response.Clear();
        Response.Buffer = true;
        Response.AddHeader("content-disposition", "attachment;filename=UserExport-" + DateTime.Now.ToString("dd_MM_yyyy_HH_mm_ss") + ".csv");
        Response.Charset = "";
        Response.ContentType = "application/text";
        Response.Output.Write(GetCsv(childItemList));
        ExportButton.Enabled = true;
        SummaryLiteral.Text = "Successfully finished export.";
        Response.Flush();
        Response.End();
    }
    catch (System.Threading.ThreadAbortException)
    {
        // exception can be ignored
    }
    catch (Exception ex)
    {
        Response.Write(ex.ToString());
        SummaryLiteral.Text = "Error occured during export.";
    }
}