===========IDBHelper.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Data;
using System.Data.Common;
using System.Data.OracleClient;

namespace DAL
{
    public interface IDBHelper
    {
        void getConn();
        void openConn();
        void closeConn();
        void beginTrans();
        void commitTrans();
        void rollbackTrans();
        object execScalar(string sql);
        void execSql(string sql);
        int execSql(string sql, OracleParameter[] para);
        int execSqlREF(string sql);
        int execSqlREF(string sql, OracleParameter[] para);
        DataSet getDataSet(string sql);
        DataSet getDataSet(string sql, OracleParameter[] para);
    }
}

===========繼承類DBHelperORACLE
using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;
using System.Data;
using System.Data.OracleClient;
using System.Data.Common;

namespace DAL
{
    public class DBHelperORACLE : IDBHelper
    {
        public OracleConnection conn = null;
        private OracleCommand cmd = null;
        private OracleDataAdapter adapter = null;
        private bool isTrans = false;
        private OracleTransaction trans = null;

        public DBHelperORACLE() { }
        /**
         * 獲取資料庫連線物件
         * */
        public void getConn()
        {
            String connStr = ConfigurationManager.AppSettings["DB"].ToString();
            this.conn = new OracleConnection(connStr);
        }
        /**
         * 開啟資料庫連線
         * */
        public void openConn()
        {
            this.getConn();
            if ((this.conn != null) && (this.conn.State == ConnectionState.Closed))
            {
                this.conn.Open();
            }
        }
        /**
         *  關閉資料庫連線
         * */
        public void closeConn()
        {
            if ((this.conn != null) && (this.conn.State != ConnectionState.Closed) && !this.isTrans)
            {
                this.conn.Close();
            }
        }
        /**
         * 開始事務
         * */
        public void beginTrans()
        {
            this.openConn();
            this.isTrans = true;
            this.trans = this.conn.BeginTransaction();
        }
        /**
         * 提交事務
         * */
        public void commitTrans()
        {
            this.trans.Commit();
            this.isTrans = false;
            this.closeConn();
        }
        /**
         * 回滾事務
         * */
        public void rollbackTrans()
        {
            this.trans.Rollback();
            this.isTrans = false;
            this.closeConn();
        }
        /**
         * 執行DML語句
         * */
        public void execSql(string sql)
        {
            if (this.isTrans)
            {
                this.cmd = conn.CreateCommand();
                this.cmd.Transaction = this.trans;
            }
            else
            {
                this.openConn();
                this.cmd = conn.CreateCommand();
            }

            this.cmd.CommandText = sql;
            this.cmd.ExecuteNonQuery();
            this.closeConn();
        }
        /**
         * 執行DML語句（可帶引數）
         * */
        public int execSql(string sql, OracleParameter[] para)
        {
            if (this.isTrans)
            {
                this.cmd = conn.CreateCommand();
                this.cmd.Transaction = this.trans;
            }
            else
            {
                this.openConn();
                this.cmd = conn.CreateCommand();
            }

            this.cmd.CommandText = sql;
            for (int i = 0; i < para.Length; i++)
            {
                this.cmd.Parameters.Add(para[i]);
            }
            int result = this.cmd.ExecuteNonQuery();
            this.closeConn();
            return result;
        }
        /**
         * 執行DML語句，並返回單獨一列的值
         * */
        public object execScalar(string sql)
        {
            if (this.isTrans)
            {
                this.cmd = conn.CreateCommand();
                this.cmd.Transaction = this.trans;
            }
            else
            {
                this.openConn();
            }
            this.cmd = conn.CreateCommand();
            this.cmd.CommandText = sql;
            object returnval=cmd.ExecuteScalar();
            this.closeConn();
            return returnval;
        }
        /**
         * 執行DML語句，並返回影響行數
         * */
        public int execSqlREF(string sql)
        {
            int J;
            if (this.isTrans)
            {
                this.cmd = conn.CreateCommand();
                this.cmd.Transaction = this.trans;
            }
            else
            {
                this.openConn();
                this.cmd = conn.CreateCommand();
            }

            this.cmd.CommandText = sql;
            J = this.cmd.ExecuteNonQuery();
            this.closeConn();
            return J;
        }
        /**
         * 執行DML語句（可帶引數）並返回影響行數
         * */
        public int execSqlREF(string sql, OracleParameter[] para)
        {
            int J = 0;
            if (this.isTrans)
            {
                this.cmd = conn.CreateCommand();
                this.cmd.Transaction = this.trans;
            }
            else
            {
                this.openConn();
                this.cmd = conn.CreateCommand();
            }
            this.cmd.CommandText = sql;
            if (para != null)
            {
                for (int i = 0; i < para.Length; i++)
                {
                    this.cmd.Parameters.Add(para[i]);
                }
            }
            J = this.cmd.ExecuteNonQuery();
            this.closeConn();
            return J;
        }
        /**
         * 通過SQL語句返回結果集
         * */
        public System.Data.DataSet getDataSet(string sql)
        {
            DataSet dataSet = new DataSet();
            if (this.isTrans)
            {
                this.cmd = conn.CreateCommand();
                this.cmd.Transaction = this.trans;
            }
            else
            {
                this.openConn();
                this.cmd = conn.CreateCommand();
            }
            cmd.CommandText = sql;
            adapter = new OracleDataAdapter(cmd);
            adapter.Fill(dataSet);
            this.closeConn();
            return dataSet;
        }
        /**
        * 通過SQL語句返回結果集
        * */
        public System.Data.DataSet getDataSet(string sql, OracleParameter[] para)
        {
            DataSet dataSet = new DataSet();
            try
            {
                if (this.isTrans)
                {
                    this.cmd = conn.CreateCommand();
                    this.cmd.Transaction = this.trans;
                }
                else
                {
                    this.openConn();
                }
                this.cmd = getSqlCmd(sql, para);
                adapter = new OracleDataAdapter(cmd);
                adapter.Fill(dataSet);
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                this.conn.Close();
            }
            return dataSet;
        }
        /**
        * 過濾SQL語句
        * */
        private string GetSqlStr(string strSql)
        {
            int startIndex = 0;
            int num2 = 0;
            while (startIndex < strSql.Length)
            {
                char ch = strSql[startIndex];
                if (ch.ToString() == "?")
                {
                    strSql = strSql.Remove(startIndex, 1).Insert(startIndex, ":p" + num2.ToString());
                    num2++;
                }
                startIndex++;
            }
            return strSql;
        }
        /**
         * 將引數傳入Command物件後返回該Command物件
         **/
        private OracleCommand getSqlCmd(string sql, OracleParameter[] para)
        {
            OracleCommand command = conn.CreateCommand();
            command.CommandText = sql;
            for (int i = 0; i < para.Length; i++)
            {
                command.Parameters.Add(para[i]);
            }
            return command;
        }
    }
}

===========DBFactory 工廠類
using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;

namespace DAL
{
    public class DBFactory
    {
        private  IDBHelper dbhelper;
        public  IDBHelper getDBFactory()
        {
            try
            {
                //獲取當前的資料庫型別
                string dbType = ConfigurationManager.AppSettings["DBTYPE"].ToString();
                if (dbType == "ORACLE")
                {
                    dbhelper = new DBHelperORACLE();
                    return dbhelper;
                }
                return null;
            }
            catch
            {
                return null;
            }
        }
    }
}