正则表达式获取全路径文件名

Match m = Regex.Match(@"D:\MassSendingSms\\MassSendingSms\\2d346b2d-f235-4256-be7c-e6f3471343d3.txt", "[C|D|E|F]:([\\\\]{1,2}[a-zA-Z0-9]+[\\\\]{1,2})+([a-zA-Z0-9-]+)[\\.txt]"