让Updatepanel中的控件触发整个页面Postback

GridView被Updatepanel包起来了，但是GridView上有一个Download的ImageButton, 局部刷新的话，无法下载文件， 所以用下面代码注册updatepanel中的download button每次点击都整个页面postback。

for (int i = 0; i < this.GridViewSOPDocument.Rows.Count; i++)
            {
                ImageButton imageButtonDownload = (ImageButton)this.GridViewSOPDocument.Rows[i].FindControl("ImageButtonDownload");
                if (imageButtonDownload != null)
                {
                    ((ScriptManager)((VPJQueryMaster)this.Master).FindControl("ScriptManager1")).RegisterPostBackControl(imageButtonDownload);
                }
            }

Download方法：

public void FileDownload(string filePath, string fileName, string systemFileName)
        {
            FileInfo DownloadFile
                    = new FileInfo(this.ApplicationPhysicalPath + filePath + "\\" + systemFileName);
            if (DownloadFile.Exists)
            {
                Response.Clear();
                Response.ClearHeaders();
                Response.Buffer = false;
                Response.ContentType = "application/octet-stream";
                Response.AppendHeader("Content-Disposition", "attachment;filename="
                    + HttpUtility.UrlDecode(fileName, System.Text.Encoding.UTF8));
                Response.AppendHeader("Content-Length", DownloadFile.Length.ToString());
                Response.WriteFile(DownloadFile.FullName);
                Response.Flush();
                Response.End();
            }
            else
            {
                ShowAjaxMessage("msg_public_download_file_does_not_exist");
            }
        }