C#数据库访问之DbHelper类

===========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);
    }
}

===========继承类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() { }
        /**
         * 获取数据库连接对象
         * */
        public void getConn()
        {
            String connStr = ConfigurationManager.AppSettings["DB"].ToString();
            this.conn = new OracleConnection(connStr);
        }
        /**
         * 打开数据库连接
         * */
        public void openConn()
        {
            this.getConn();
            if ((this.conn != null) && (this.conn.State == ConnectionState.Closed))
            {
                this.conn.Open();
            }
        }
        /**
         *  关闭数据库连接
         * */
        public void closeConn()
        {
            if ((this.conn != null) && (this.conn.State != ConnectionState.Closed) && !this.isTrans)
            {
                this.conn.Close();
            }
        }
        /**
         * 开始事务
         * */
        public void beginTrans()
        {
            this.openConn();
            this.isTrans = true;
            this.trans = this.conn.BeginTransaction();
        }
        /**
         * 提交事务
         * */
        public void commitTrans()
        {
            this.trans.Commit();
            this.isTrans = false;
            this.closeConn();
        }
        /**
         * 回滚事务
         * */
        public void rollbackTrans()
        {
            this.trans.Rollback();
            this.isTrans = false;
            this.closeConn();
        }
        /**
         * 执行DML语句
         * */
        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();
        }
        /**
         * 执行DML语句（可带参数）
         * */
        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;
        }
        /**
         * 执行DML语句，并返回单独一列的值
         * */
        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;
        }
        /**
         * 执行DML语句，并返回影响行数
         * */
        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;
        }
        /**
         * 执行DML语句（可带参数）并返回影响行数
         * */
        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;
        }
        /**
         * 通过SQL语句返回结果集
         * */
        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;
        }
        /**
        * 通过SQL语句返回结果集
        * */
        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;
        }
        /**
        * 过滤SQL语句
        * */
        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;
        }
        /**
         * 将参数传入Command对象后返回该Command对象
         **/
        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 工厂类
using System;
using System.Collections.Generic;
using System.Text;
using System.Configuration;

namespace DAL
{
    public class DBFactory
    {
        private  IDBHelper dbhelper;
        public  IDBHelper getDBFactory()
        {
            try
            {
                //获取当前的数据库类型
                string dbType = ConfigurationManager.AppSettings["DBTYPE"].ToString();
                if (dbType == "ORACLE")
                {
                    dbhelper = new DBHelperORACLE();
                    return dbhelper;
                }
                return null;
            }
            catch
            {
                return null;
            }
        }
    }
}

参照链接：
http://www.cnblogs.com/blsong/archive/2010/10/19/1855614.html
http://www.cnblogs.com/springyangwc/archive/2011/03/23/1993061.html
http://blog.csdn.net/nick4/article/details/2421823