without textbox search inside gridview

If gridview has focus, use keydown to filter the grid. Use timer to clear the search term (since you have no UI to clear).

Note that this is not a good feature / design as there are no clues to users that could help them. How would they even know they can search the grid?

Imagine simple typing error and confusion why the grid is empty for common search term. Add the textbox, put a small button next to it and react on enter or button click. Or add empty row at the top and filter by the column and typed text. Make the search visible somehow.

idea is good...but add some thing to make it better as Sinisa advised. And Grid key down will do the work...