C#如何判断文件下载是否成功

System.IO.FileInfo toDownload = new System.IO.FileInfo(url路径);
Response.Clear();
Response.AddHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(toDownload.Name));         
Response.ContentType = "application/x-zip-compressed";
Response.TransmitFile(url路径);
Response.End();

可是成功下载,但没办法统计用户是否下载成功.要做有效的统计次数.

请高手帮忙解答.

谢谢 --------------------编程问答-------------------- System.IO.FileInfo   toDownload   =   new   System.IO.FileInfo(url路径); 
Response.Clear(); 
Response.AddHeader("Content-Disposition",   "attachment;filename="   +   HttpUtility.UrlEncode(toDownload.Name));                   
Response.ContentType   =   "application/x-zip-compressed"; 
Response.TransmitFile(url路径); 
Response.End(); <-----运行到这里不就成功了吗?
在这之后进行count++的操作 --------------------编程问答-------------------- 运行是成功了
用户要是点取消
count++
也会执行的 --------------------编程问答-------------------- if(File.Exists(Path))
   下載成功 --------------------编程问答-------------------- if(File.Exists(Path)) 
{
   "成功"
}

补充：.NET技术 ,  C#