void bookGenerateId() { string OID = "select BOOK_ID from BOOK ORDER BY BOOK_ID"; string BName; int BID; string format = "0000000"; SqlDataAdapter ad = new SqlDataAdapter(OID, consql); DataSet ds = new DataSet(); ad.Fill(ds, "Book"); if (ds.Tables["Book"].Rows.Count > 0) { BName = ds.Tables["Book"].Rows[ds.Tables["Book"].Rows.Count - 1][0].ToString(); BID = int.Parse(BName.Substring(1, (BName.Length - 1))); bookID = "B" + ((BID + 1).ToString(format)); } else { bookID = "B0000001"; } }