Saving DataGridView content into a file

Question

Hi,

I have made a windows Application which gets some information from user and puts them in DataGridView rows.

I want to save the table content into a file which can be opened only by my own application, not other softwares like notepad, etc. 

How can I do that? Is it possible to save them to a file with an unnown suffix like .jss or something like that?

I need a tutorial for this task. I use C#.

Please help me.

Thanks.