不支持GridView导出到PDF错误

Question

以下是 Export ActionResult 到 PDF ：

List<DailySum> lstDailySum = db.DailySum.Include(x => x.codeACl).Include(x => x.codeCou).Include(x => x.codeAgc).Include(x => x.AInfo).ToList();

GridView gv = new GridView();
if (Session["Paging"] == null)
{
    gv.DataSource = lstDailySum;
}
else
{
    gv.DataSource = Session["Paging"];
}

gv.DataBind();
Response.ClearContent();
Response.Buffer = true;
Response.AddHeader("content-disposition", "attachment; filename=DailySumExport.pdf");
Response.ContentType = "application/pdf";
Response.Charset = "";
StringWriter sw = new StringWriter();
HtmlTextWriter htw = new HtmlTextWriter(sw);
gv.RenderControl(htw);
Response.Output.Write(sw.ToString());
Response.Flush();
Response.End();

现在，当我尝试导出到Excel时，此功能正常，但当我尝试导出为PDF时，我收到此错误消息：

  

Adob​​e Acrobat Reader DC无法打开＆＃39; DailySumExport.pdf＆＃39;因为它不支持文件类型或文件已损坏（例如，它是作为电子邮件附件发送的，并且未正确解码）。

非常感谢有关如何解决此问题的任何帮助。

感谢。