Request.ApplicationPath  返回/或者iis下目录。如果个人网站是在iis网站下面新建的目录aaa，返回如：/aaa

Request.Url.Authority  返回域名和端口或ip  如：localhost:1897

var applicationPath =Request.ApplicationPath.Length>1 ? Request.ApplicationPath :"";//防止多一个斜线。当是网站时候，返回/aaa 。当是网站下的目录，返回空字符

var path ="http://"+Request.Url.Authority+applicationPath +"/upload/文件.txt"; //最终：http://localhost:1897/upload/文件.txt 或http://localhost:1897/aaa/upload/文件.txt