Auto Generate Number using C# ASP.NET Program

query = "Select Distinct TransmittleNo as TransNo from Temp_Doc Order By TransmittleNo";
                   ds = null;
                   ds = con.get_records(query);
                   if (ds.Tables[0].Rows.Count > 0)
                   {
                       for (int inti = 0; inti < ds.Tables[0].Rows.Count; inti++)
                       {
                       strTransmittleNo = ds.Tables[0].Rows[0]["TransNo"].ToString();
                       //strTransmittleSeq = "0";
                       strPentaTransmittleNo = "";

                       query = "Select decode(max(TransmittleSeq)+1,null,1,max(TransmittleSeq)+1) as TransSeqNo from T_Doc_Control Where TransmittleNo = '" + strTransmittleNo + "' And TransmittleDate = '" + strIssueDate.Trim()  + "' And TransmittleSeq is not null"; // +strTransmittleNo + "'";
                       dsGrid = null;
                       dsGrid = con.get_records(query);
                       if (dsGrid.Tables[0].Rows.Count > 0)
                       {
                           strPentaTransmittleNo = "PGM-TransmittleNo-" + dsGrid.Tables[0].Rows[0]["TransSeqNo"].ToString();
                           strTransmittleSeq = dsGrid.Tables[0].Rows[0]["TransSeqNo"].ToString();
                       }

                       query = "Update T_DOC_Control set PentaTransmittleNo = '" + strPentaTransmittleNo + "',";
                       query = query + "TransmittleSeq = " + strTransmittleSeq + " ";
                       query = query + "Where TransmittleNo = '" + strTransmittleNo + "' And PentaTransmittleNo IS NULL";
                       intResult = con.insert_records(query);
                       }
                   }