Export DataGridView headers

Through a datagridview I generate a TXT file where it only throws me the results How to export headers?

TextWriter writer = new StreamWriter(@"C:\test\guest.txt");

            for (int i = 0; i < dataGridView2.Rows.Count -1 ; i++) 
            {
                writer.WriteLine("======================================================================================");
                for (int j = 0; j < dataGridView2.Columns.Count; j++)
                {
                    writer.Write("\t" + dataGridView2.Rows[i].Cells[j].Value.ToString() + "\t" + "|");
                }
                writer.WriteLine("");
                writer.WriteLine("======================================================================================");
            }
            writer.Close();