how to mark as read only the last row of DataGridView ?

Question

i'm displaying the values in last row of datagridview. but when i click on last row, the values are disappear. i jast want it stable after clicking on it (i.e. on last row).

For stable i use this below code but it's not working

dataGridView1.Rows[dataGridView1.Rows.Count - 1].ReadOnly = true;

so suggest me how can i solve it ?