asp.net 下载文件
 
       //源文件名称

       //提供下载的文件，不编码的话文件名会乱码   
        //private string fileName = HttpContext.Current.Server.UrlEncode("规范.rar");  

        string fileName = @"D:\我的文档\Visual Studio 2010\WebSites\WebSite14\a00.zip";   
        FileInfo info = new FileInfo(fileName);
        long fileSize = info.Length;
        Response.Clear();
        Response.ContentType = "application/octet-stream";
        Response.AddHeader("Content-Disposition", "attachement;filename=" + "您希望显示的文件名称.rar"); //这里的文件名称也应该编码
        //指定文件大小   
        Response.AddHeader("Content-Length", fileSize.ToString());
        Response.WriteFile(fileName, 0, fileSize);
        Response.Flush();
        Response.Close();