c#中如何循环读取文本文件中 2个指定字符之间的内容？

比如我本地有一个文本文档，里面的内容如下：
@@@               3  3        ###@@@               8  8        ###@@@               8  8        ###@@@               0  0        ###@@@               6  6        ###@@@               6  6        ###@@@               1  1        ###@@@               6  6        ###@@@               3  3        ###@@@               1  1        ###@@@               0  0        ###@@@               9  9        ###@@@               5  5        ###@@@               7  7        ###@@@               9  9        ###@@@               8  8        ### @@@               3  3