Question

How do I make the datagridview line text in bold when I pick a row?

Answer 1

Handle the CellFormatting event of the DataGridView and apply a bold style to the font if the cell belongs to a selected row:

private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
{
  var dataGridView = sender as DataGridView;
  if (dataGridView.Rows[e.RowIndex].Selected)
  {
    e.CellStyle.Font = new Font(e.CellStyle.Font, FontStyle.Bold);
    // edit: to change the background color:
    e.CellStyle.SelectionBackColor = Color.Coral;
  }
}