//判断表是否存在

        public static bool IsExist(string tablename, OracleConnection strconn)

        {

            String tableNameStr = "select count(*) from user_tables where table_name ='" + tablename.ToUpper() + "'";

            OracleCommand cmd = new OracleCommand(tableNameStr, strconn);

            int result =Convert.ToInt32(cmd.ExecuteScalar());

            if (result == 0)

            {

                return false;

            }

            else

            {

                return true;

            }

        }