怎么下载不确定类型文件？

Question

这是我下载的Code 
  string invoiceNo = e.CommandArgument.ToString();
                    DataRow drFile = Contract_TransportFilesAdapter.GetDataByInvoiceNoKey(invoiceNo).Rows[0];
                    string strFileName = invoiceNo + "_运单";
                    Response.Buffer = true;
                    Response.Clear();
                    Response.ContentType = drFile["FILE1_TYPE"].ToString();
                    Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(strFileName));
                    Response.BinaryWrite((Byte[])drFile["FILE1"]);
                    Response.End();
但会出现文件名乱码情况，而且只回来浏览器里出现。FILE1_TYPE是数据库表的字段：纪录是：image/gif  或者application/pdf等等作为参考，以下是我上传写的代码：
              string strType1 = UploadFile1.ContentType;
                byte[] byteData1 = new byte[intLen1];                Stream objStream1 = UploadFile1.InputStream;                objStream1.Read(byteData1, 0, intLen1);
               
                rowFile.INVOICENO = invoriceNo;
                rowFile.FILE1 = byteData1;
                rowFile.FILE1_TYPE = strType1;
                rowFile.FILE1_LENGTH = intLen1;
              
                bool blnNew = new ContractData().AddTransportFile(rowFile, guidUserId);//Insert进数据库

Answer 1

 protected void downloadfile(string filename)
 {
 string FullFileName = "d:\\111.zip";
 FileInfo DownloadFile = new FileInfo(FullFileName);
 Response.Clear();
 Response.ClearHeaders();
 Response.Buffer = false;
 Response.ContentType = "application/octet-stream";
 Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(DownloadFile.FullName, System.Text.Encoding.UTF8));
 Response.AppendHeader("Content-Length", DownloadFile.Length.ToString());
 Response.WriteFile(DownloadFile.FullName);
 Response.Flush();
 Response.End();  
 }