ASP.NET 下載文件

/**//// <summary>
        /// 下載文件
        /// </summary>
        /// <param name="filepath"></param>
        public static void DownloadFile(string filepath)
        ...{
            string    strContentType    = "";
            string    strFileName        = "";
            string    strFilePath        = "";
            int        intIndex1        = -1;
            int        intIndex2        = -1;
            int        intIndex        = 0;

            if (filepath.EndsWith(".doc"))
            ...{
                strContentType = "application/msWord";
            }
            else&nb

sp;if (filepath.EndsWith(".xls"))
            ...{
                //strContentType = "application/x-zaurus-xls"
                strContentType = "application/vnd.ms-Excel";
            }
            else if (filepath.EndsWith(".pdf"))
            ...{
                strContentType = "application/pdf";
            }
            else if (filepath.EndsWith(".PPT"))
            ...{
                //strContentType = "application/PowerPoint"
                strContentType = "application/vnd.ms-PowerPoint";
            }
            else if (filepath.EndsWith(".jpg") || filepath.EndsWith(".jpeg") || filepath.EndsWith(".jpe"))
  ...{
                strContentType = "image/jpeg";
            }
            else if (filepath.EndsWith(".bmp"))
            ...{
                strContentType = "image/bmp";
            }
            else if (filepath.EndsWith(".gif"))
            ...{
                strContentType = "image/gif";
            }
            else if (filepath.EndsWith(".zip"))
            ...{
                strContentType = "application/zip";
            }
            else if (filepath.EndsWith(".txt"))
  ...{
                strContentType = "text/plain";
            }
            else
            ...{
                strContentType = "application/octet-stream";
            }

            intIndex1 = filepath.LastIndexOf("/");
            intIndex2 = filepath.LastIndexOf("\");

            if (intIndex1 > intIndex2)
            ...{
                intIndex = intIndex1;
            }
            else
            ...{
                intIndex = intIndex2;
         &nbsp;  }

            if (intIndex > -1)
            ...{
                if (intIndex + 1 < filepath.Length)
                    strFileName = filepath.Substring(intIndex + 1);
            }
            else
            ...{
                strFileName = filepath;
            }

            // 文件路經処理 
            if (filepath.StartsWith("/") || filepath.StartsWith("\"))
                strFilePath = HttpContext.Current.Server.MapPath("/") + filepath;
            else
                strFilePath = filepath;

            if (FileUtil.isFileExist(strFilePath))
            ...{
  HttpContext.Current.Response.Clear();
                HttpContext.Current.Response.ContentType = strContentType;
                HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(strFileName));

                HttpContext.Current.Response.WriteFile(strFilePath);
                //HttpContext.Current.Response.BinaryWrite(objFileIO.IFileByte(strFilePath));

                //HttpContext.Current.Response.End();
                HttpContext.Current.Response.Flush();
                HttpContext.Current.Response.Close();
            }
            else
            ...{
                SetGlobalMessageID(FindKeyValueCutNull(GXML.COMMONMESSAGE, GXML.DOWNLOAD_FILE_NOEXIST));
            }
            
            //Call response.BinaryWrite(objFileIO.IFileByte(filepath))
        }