asp 实现文件下载代码

很好的一个ASP文件下载代码，拿出来分享。
dim filepath,filename,filefolder
filename = trim(request("filename"))
filefolder = "download" '下载文件所在的目录 结尾不加/
filepath = filefolder&"/"&filename
Response.AddHeader "Content-Disposition","attachment;filename="&filename&"" '下载时重新命名文件 Response.buffer = True ’开启缓存
Response.ContentType = "audio/x-pn-realaudio" ‘文件类型
Dim objStream
Set objStream = Server.CreateObject("ADODB.Stream") ’创建ADODB.stream对象
objStream.Type = 1 ’以二进制读取模式
objStream.Open
objStream.LoadFromFile filepath ’读取文件
Response.binarywrite objStream.Read ’以二进制的方式输出至客户端浏览器
response.Flush() ’边缓存边输出
Session("afon")=false ’重新设置session为FALSE
objStream.Close
Set objStream = Nothing
附常见的contenttype类型
<%
Function Get_FileTypeAbName(sFileType)
select case sFileType
’图像类
Case "image/gif"
Get_FileTypeAbName="gif"
exit function
Case "image/pjpeg"
Get_FileTypeAbName="jpg"
exit Function
Case "image/bmp"
Get_FileTypeAbName="bmp"
exit Function
Case "image/png"
Get_FileTypeAbName="png"

exit Function
Case "image/tif"
Get_FileTypeAbName="tif"
Exit Function
’音频类
Case "audio/mpeg"
Get_FileTypeAbName="mp3"
Exit Function
Case "audio/x-ms-wma"
Get_FileTypeAbName="wma"
Exit Function
Case "audio/mid"
Get_FileTypeAbName="mid"
Exit Function
Case "audio/wav"
Get_FileTypeAbName="wav"
Exit Function
’视频类
Case "application/vnd.rn-real media"
Get_FileTypeAbName="rm"
Exit Function
Case "video/x-ms-wmv"
Get_FileTypeAbName="wmv"
Exit Function
’flash
Case "application/x-shockwave-flash"
Get_FileTypeAbName="swf"
Exit Function
’压缩软件类
Case "application/x-zip-compressed"
Get_FileTypeAbName="zip"
Exit Function

Case "application/octet-stream"
Get_FileTypeAbName="rar"
Exit Function
’文本类
Case "text/plain"
Get_FileTypeAbName="txt"
Exit Function
Case "text/html"
Get_FileTypeAbName="html"
Exit Function
Case "application/msaccess"
Get_FileTypeAbName="mdb"
Exit Function
Case "application/msword"
Get_FileTypeAbName="doc"
Exit Function
Case "application/vnd.ms-excel"
Get_FileTypeAbName="xls"
Exit Function
end select
End Function
%>