Working with an array whose number of rows reaches tens of thousands may be troublesome. Adding the ability to automatically scroll through the array to the appropriate line could facilitate this work, especially if the points to which the scroll will not be accidental. The following code allows you to scroll the table to the selected line.

dataGridView.ClearSelection();>
dataGridView.Rows[nr_wiersza].Selected = true;
dataGridView.FirstDisplayedScrollingRowIndex  = nr_wiersza;