当每个文件上传后会触发UploaderBase.FileUploaded事件，如果同时上传三个文件，那么该事件会触发三次。如果想在所有的文件上传完成后执行，就需要使用UploaderBase.UploadCompleted事件。
Example：
Protected void Uploader1_UploadCompleted(object sender,UploaderEventArgs[] args)
{
string msg = "You have uploaded "+args.Length+" files";
foreach(UploaderEventArgs arg in args)
{
Msg +="\r\n" +arg.FileName+","+arg.FileSize;
}
}