<pre name="code" class="csharp">string path = Server.MapPath("aa\\ahaakladahsasdas_bb.zip"); 
            string newfileName = ""; 
            if (File.Exists(path)) 
            { 
                FileInfo fi = new FileInfo(path); 
                Response.Clear();//Clear 方法删除缓冲区中的所有 HTML 输出。但 Clear 方法只删除响应正文 
                //而不删除响应标题。可以用该方法处理错误情况。 
                Response.ClearHeaders(); 
                Response.Buffer = false;//这句话的意思就是指明输出页面是否被缓冲，当属性值为True时， 
                //服务器将不会向客户端发送任何信息，直到所有程序执行完或者遇到  
                //Response.Flush或Response.End语句，才会释放缓冲区的信息。 
                string filename = Path.GetFileName(path); 
                newfileName = newfileName + filename.Substring(filename.LastIndexOf(".")); 
                Response.Clear(); 
                Response.ClearHeaders(); 
                Response.Buffer = false; 

                newfileName = HttpUtility.UrlEncode(newfileName);// 这一步弹出下载保存的对话框，出现文件名乱码，但变量中的文件名是正常的。   
                Response.AppendHeader("Content-Disposition", "attachment;filename=" + newfileName);//为用户保存文件是显示的名称 
                //告诉客户端这个响应内容的类型为attachment 你是通过Response.AppendHeader("content-type", "attachment"); 申明的。 

                Response.AppendHeader("Content-Length", fi.Length.ToString()); 
                Response.ContentType = "application/octet-stream"; 
                Response.WriteFile(newfileName);//用response来返回文件的路径   
                Response.Flush();//清空response   
                Response.End(); 
                //Response.End(); 如果抛异常的话可使用 
                //HttpContext.Current.ApplicationInstance.CompleteRequest(); 
            } 
            else 
            { 
                Response.Write("<script langauge=javascript>alert(‘文件不存在!');</script>"); 
            }