Datagridview logical - puting back color in datagridview

while (dr.Read())
            {

                int id = dr.GetInt32(0);
                DateTime startBook = dr.GetDateTime(2);
                DateTime endBook = dr.GetDateTime(3);

                int startBook_C = startBook.Day;
                int endBook_C = endBook.Day;

                int TotalDays = endBook_C - startBook_C;

                //dataGridView1(startBook_C, id - 1).Style.BackColor = Color.Blue;
                dataGridView1.Rows[startBook_C].Cells[endBook_C-1].Style.BackColor = Color.Blue;
                int i;
                for (i = 1; i <= TotalDays; i++)
                {
                    dataGridView1.Rows[startBook_C + i].Cells[endBook_C -1].Style.BackColor = Color.Blue;
                    //dataGridView1.Rows[startBook_C].Cells[carID - 1].Style.BackColor = Color.Blue;
                    // dataGridView1(startBook_C + i, id - 1).Style.BackColor = Color.Red;/* TODO ERROR: Skipped SkippedTokensTrivia */
                    TotalDays -= 1;
                }



            }
            Con.Close();