how store the textbox values in datagrid view with out using database connection

The datagridview is a display container and does not store values (except in memory).

If you want to store/persist the data, you're going to need to either save to a database (which you're saying you don't want to do) or perhaps save it in a text file.

There is a CodeProject article on using CSV: C# class library for exporting data to CSV/Excel file[^]

Hope this helps to get you started.

Cheers.