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 方法刪除緩沖區中的所有 HTML 輸出。但 Clear 方法只刪除響應正文 
                //而不刪除響應標題。可以用該方法處理錯誤情況。 
                Response.ClearHeaders(); 
                Response.Buffer = false;//這句話的意思就是指明輸出頁面是否被緩沖，當屬性值為True時， 
                //服務器將不會向客戶端發送任何信息，直到所有程序執行完或者遇到  
                //Response.Flush或Response.End語句，才會釋放緩沖區的信息。 
                string filename = Path.GetFileName(path); 
                newfileName = newfileName + filename.Substring(filename.LastIndexOf(".")); 
                Response.Clear(); 
                Response.ClearHeaders(); 
                Response.Buffer = false; 

                newfileName = HttpUtility.UrlEncode(newfileName);// 這一步彈出下載保存的對話框，出現文件名亂碼，但變量中的文件名是正常的。   
                Response.AppendHeader("Content-Disposition", "attachment;filename=" + newfileName);//為用戶保存文件是顯示的名稱 
                //告訴客戶端這個響應內容的類型為attachment 你是通過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來返回文件的路徑   
                Response.Flush();//清空response   
                Response.End(); 
                //Response.End(); 如果拋異常的話可使用 
                //HttpContext.Current.ApplicationInstance.CompleteRequest(); 
            } 
            else 
            { 
                Response.Write("script langauge=javascript>alert(‘文件不存在!');/script>"); 
            }