Error - GridView' does not contain a definition for 'SelectedRows'

Hi

Error    CS1061    'GridView' does not contain a definition for 'SelectedRows' and no accessible extension method 'SelectedRows' accepting a first argument of type 'GridView' could be found (are you missing a using directive or an assembly reference?)    LMS    D:\GitHub\Admin\ReportSessionBooksPlanning.aspx.cs    263    Active
 

private void dataGridView1_MouseDoubleClick(object sender, MouseEventArgs e)
        {
            var value = grdPlanning.SelectedRows[0].Cells[0].ToString();
        }

Thanks