2.0下载：
string fileName = "tempimg.jpg"; //下载到客户端后的文件
string filePath = Server.MapPath("../imgs/img7.jpg"); //要下载的服务器的文件路径
FileInfo fileInfo = new FileInfo(filePath);
Response.Clear();
Response.ClearContent();
Response.ClearHeaders();
Response.Buffer = true; //设置文档缓存
Response.AddHeader("Content-Disposition","attachment;filename="+fileName);
Response.AddHeader("Content-Length",fileInfo.Length.ToString());
Response.AddHeader("Content-Transfer-Encoding","binary");
Response.ContentType = "application/octet-stream";
Response.ContentEncoding = System.Text.Encoding.GetEncoding("UTF-8");
Response.WriteFile(fileInfo.FullName);
Response.Flush();
Response.End();
3.5下载：
string fileName = "tempimg.jpg"; //下载到客户端后的文件
string filePath = Server.MapPath("../imgs/img7.jpg"); //要下载的服务器的文件路径
Response.Clear();
Response.Buffer = true; //设置文档缓存
Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
Response.ContentType = "application/unknown";
Response.TransmitFile(filePath);
Response.End();
本文出自 “风中寻觅” 博客，谢绝转载！
原文：http://xingcheng.blog.51cto.com/3693811/1731556