DBHelper的两种实现方式

Method 1.

According to the abstract class of ADO.NET,accomplish the core code of ADO.NET,named DBHelper.

Then generate a concrete database ADO.NET object using factory,as the below showing.

public class DBHelper
    {
        //获取数据库类型
        private static string strDbType = CommonUtils.GetConfigValueByKey("dbType").ToUpper();

        //将数据库类型转换成枚举类型
        public static DatabaseType DbType = DatabaseTypeEnumParse<DatabaseType>(strDbType);       

        //获取数据库连接字符串
        public static string ConnectionString = GetConnectionString("connectionString");

        //获取数据库命名参数符号，比如@(SQLSERVER)、:(ORACLE)
        public static string DbParmChar = DbFactory.CreateDbParmCharacter();
        
        private static Hashtable parmCache = Hashtable.Synchronized(new Hashtable());

        /// <summary>
        ///通过提供的参数，执行无结果集的数据库操作命令
        /// 并返回执行数据库操作所影响的行数。
        /// </summary>
        /// <param name="connectionString">数据库连接字符串</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行<</param>
        /// <param name="commandParameters">执行命令所需的参数数组</param>
        /// <returns>返回通过执行命令所影响的行数</returns>
        public static int ExecuteNonQuery(string connectionString, CommandType cmdType, string cmdText, params IDbDataParameter[] commandParameters)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();

            using (IDbConnection conn = DbFactory.CreateDbConnection(connectionString))
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                int val = cmd.ExecuteNonQuery();
                cmd.Parameters.Clear();
                return val;
            }
        }
        /// <summary>
        ///通过提供的参数，执行无结果集的数据库操作命令
        /// 并返回执行数据库操作所影响的行数。
        /// </summary>
        /// <param name="connectionString">数据库连接字符串</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行<</param>
        /// <returns>返回通过执行命令所影响的行数</returns>
        public static int ExecuteNonQuery(string connectionString, CommandType cmdType, string cmdText)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();

            using (IDbConnection conn = DbFactory.CreateDbConnection(connectionString))
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, null);
                int val = cmd.ExecuteNonQuery();
                cmd.Parameters.Clear();
                return val;
            }
        }

        /// <summary>
        ///通过提供的参数，执行无结果集返回的数据库操作命令
        ///并返回执行数据库操作所影响的行数。
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="conn">数据库连接对象</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行</param>
        /// <param name="commandParameters">执行命令所需的参数数组</param>
        /// <returns>返回通过执行命令所影响的行数</returns>
        public static int ExecuteNonQuery(IDbConnection connection, CommandType cmdType, string cmdText, params IDbDataParameter[] commandParameters)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();

            PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
            int val = cmd.ExecuteNonQuery();
            cmd.Parameters.Clear();
            return val;
        }
        /// <summary>
        ///通过提供的参数，执行无结果集返回的数据库操作命令
        ///并返回执行数据库操作所影响的行数。
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="conn">数据库连接对象</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行</param>
        /// <returns>返回通过执行命令所影响的行数</returns>
        public static int ExecuteNonQuery(IDbConnection connection, CommandType cmdType, string cmdText)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();

            PrepareCommand(cmd, connection, null, cmdType, cmdText, null);
            int val = cmd.ExecuteNonQuery();
            cmd.Parameters.Clear();
            return val;
        }

        /// <summary>
        ///通过提供的参数，执行无结果集返回的数据库操作命令
        ///并返回执行数据库操作所影响的行数。
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="trans">sql事务对象</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行<</param>
        /// <param name="commandParameters">执行命令所需的参数数组</param>
        /// <returns>返回通过执行命令所影响的行数</returns>
        public static int ExecuteNonQuery(IDbTransaction trans, CommandType cmdType, string cmdText, params IDbDataParameter[] commandParameters)
        {
            IDbConnection conn = null;
            if (trans == null)
            {
                conn = DbFactory.CreateDbConnection(ConnectionString);
            }
            else 
            {
                conn = trans.Connection;
            }

            IDbCommand cmd = DbFactory.CreateDbCommand();
            PrepareCommand(cmd, conn, trans, cmdType, cmdText, commandParameters);
            int val = cmd.ExecuteNonQuery();
            cmd.Parameters.Clear();
            return val;
        }
        /// <summary>
        ///通过提供的参数，执行无结果集返回的数据库操作命令
        ///并返回执行数据库操作所影响的行数。
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  int result = ExecuteNonQuery(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="trans">sql事务对象</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行<</param>
        /// <returns>返回通过执行命令所影响的行数</returns>
        public static int ExecuteNonQuery(IDbTransaction trans, CommandType cmdType, string cmdText)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();
            PrepareCommand(cmd, trans.Connection, trans, cmdType, cmdText, null);
            int val = cmd.ExecuteNonQuery();
            cmd.Parameters.Clear();
            return val;
        }
        /// <summary>
        /// 使用提供的参数，执行有结果集返回的数据库操作命令
        /// 并返回SqlDataReader对象
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  SqlDataReader r = ExecuteReader(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">数据库连接字符串</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行<</param>
        /// <param name="commandParameters">执行命令所需的参数数组</param>
        /// <returns>返回SqlDataReader对象</returns>
        public static IDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText, params IDbDataParameter[] commandParameters)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();
            IDbConnection conn = DbFactory.CreateDbConnection(connectionString);

            //我们在这里使用一个 try/catch,因为如果PrepareCommand方法抛出一个异常，我们想在捕获代码里面关闭
            //connection连接对象，因为异常发生datareader将不会存在，所以commandBehaviour.CloseConnection
            //将不会执行。
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                IDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }
        /// <summary>
        ///使用提供的参数，执行有结果集返回的数据库操作命令
        /// 并返回SqlDataReader对象
        /// </summary>
        /// <param name="connectionString">数据库连接字符串</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行<</param>
        /// <returns>返回SqlDataReader对象</returns>
        public static IDataReader ExecuteReader(string connectionString, CommandType cmdType, string cmdText)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();
            IDbConnection conn = DbFactory.CreateDbConnection(connectionString);

            //我们在这里使用一个 try/catch,因为如果PrepareCommand方法抛出一个异常，我们想在捕获代码里面关闭
            //connection连接对象，因为异常发生datareader将不会存在，所以commandBehaviour.CloseConnection
            //将不会执行。
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, null);
                IDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
                cmd.Parameters.Clear();
                return rdr;
            }
            catch
            {
                conn.Close();
                throw;
            }
        }

        /// <summary>
        /// 查询数据填充到数据集DataSet中
        /// </summary>
        /// <param name="connectionString">数据库连接字符串</param>
        /// <param name="cmdType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="cmdText">命令文本</param>
        /// <param name="commandParameters">参数数组</param>
        /// <returns>数据集DataSet对象</returns>
        public static DataSet dataSet(string connectionString, CommandType cmdType, string cmdText, params IDbDataParameter[] commandParameters)
        {
            DataSet ds = new DataSet();
            IDbCommand cmd = DbFactory.CreateDbCommand();
            IDbConnection conn = DbFactory.CreateDbConnection(connectionString);
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, commandParameters);
                IDbDataAdapter sda = DbFactory.CreateDataAdapter(cmd);
                sda.Fill(ds);
                return ds;
            }
            catch
            {
                conn.Close();
                throw;
            }
            finally
            {
                conn.Close();
                cmd.Dispose();
            }
        }

        /// <summary>
        /// 查询数据填充到数据集DataSet中
        /// </summary>
        /// <param name="connectionString">数据库连接字符串</param>
        /// <param name="cmdType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="cmdText">命令文本</param>
        /// <returns>数据集DataSet对象</returns>
        public static DataSet dataSet(string connectionString, CommandType cmdType, string cmdText)
        {
            DataSet ds = new DataSet();
            IDbCommand cmd = DbFactory.CreateDbCommand();
            IDbConnection conn = DbFactory.CreateDbConnection(connectionString);
            try
            {
                PrepareCommand(cmd, conn, null, cmdType, cmdText, null);
                IDbDataAdapter sda = DbFactory.CreateDataAdapter(cmd);
                sda.Fill(ds);
                return ds;
            }
            catch
            {
                conn.Close();
                throw;
            }
            finally
            {
                conn.Close();
                cmd.Dispose();
            }
        }

        /// <summary>
        /// 依靠数据库连接字符串connectionString,
        /// 使用所提供参数，执行返回首行首列命令
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">数据库连接字符串</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行</param>
        /// <param name="commandParameters">执行命令所需的参数数组</param>
        /// <returns>返回一个对象，使用Convert.To{Type}将该对象转换成想要的数据类型。</returns>
        public static object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText, params IDbDataParameter[] commandParameters)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();

            using (IDbConnection connection = DbFactory.CreateDbConnection(connectionString))
            {
                PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
                object val = cmd.ExecuteScalar();
                cmd.Parameters.Clear();
                return val;
            }
        }
        /// <summary>
        /// 依靠数据库连接字符串connectionString,
        /// 使用所提供参数，执行返回首行首列命令
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="connectionString">数据库连接字符串</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行</param>
        /// <returns>返回一个对象，使用Convert.To{Type}将该对象转换成想要的数据类型。</returns>
        public static object ExecuteScalar(string connectionString, CommandType cmdType, string cmdText)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();

            using (IDbConnection connection = DbFactory.CreateDbConnection(connectionString))
            {
                PrepareCommand(cmd, connection, null, cmdType, cmdText, null);
                object val = cmd.ExecuteScalar();
                cmd.Parameters.Clear();
                return val;
            }
        }
        /// <summary>
        ///依靠数据库连接字符串connectionString,
        /// 使用所提供参数，执行返回首行首列命令
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="conn">数据库连接对象</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行</param>
        /// <param name="commandParameters">执行命令所需的参数数组</param>
        /// <returns>返回一个对象，使用Convert.To{Type}将该对象转换成想要的数据类型。</returns>
        public static object ExecuteScalar(IDbConnection connection, CommandType cmdType, string cmdText, params IDbDataParameter[] commandParameters)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();

            PrepareCommand(cmd, connection, null, cmdType, cmdText, commandParameters);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }
        /// <summary>
        ///依靠数据库连接字符串connectionString,
        /// 使用所提供参数，执行返回首行首列命令
        /// </summary>
        /// <remarks>
        /// e.g.:  
        ///  Object obj = ExecuteScalar(connString, CommandType.StoredProcedure, "PublishOrders", new SqlParameter("@prodid", 24));
        /// </remarks>
        /// <param name="conn">数据库连接对象</param>
        /// <param name="commandType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="commandText">存储过程名称或者T-SQL命令行</param>
        /// <param name="commandParameters">执行命令所需的参数数组</param>
        /// <returns>返回一个对象，使用Convert.To{Type}将该对象转换成想要的数据类型。</returns>
        public static object ExecuteScalar(IDbConnection connection, CommandType cmdType, string cmdText)
        {
            IDbCommand cmd = DbFactory.CreateDbCommand();

            PrepareCommand(cmd, connection, null, cmdType, cmdText, null);
            object val = cmd.ExecuteScalar();
            cmd.Parameters.Clear();
            return val;
        }


        /// <summary>
        /// add parameter array to the cache
        /// </summary>
        /// <param name="cacheKey">Key to the parameter cache</param>
        /// <param name="cmdParms">an array of SqlParamters to be cached</param>
        public static void CacheParameters(string cacheKey, params IDbDataParameter[] commandParameters)
        {
            parmCache[cacheKey] = commandParameters;
        }

        /// <summary>
        /// 查询缓存参数
        /// </summary>
        /// <param name="cacheKey">使用缓存名称查找值</param>
        /// <returns>缓存参数数组</returns>
        public static IDbDataParameter[] GetCachedParameters(string cacheKey)
        {
            IDbDataParameter[] cachedParms = (IDbDataParameter[])parmCache[cacheKey];

            if (cachedParms == null)
                return null;

            IDbDataParameter[] clonedParms = new IDbDataParameter[cachedParms.Length];

            for (int i = 0, j = cachedParms.Length; i < j; i++)
                clonedParms[i] = (IDbDataParameter)((ICloneable)cachedParms[i]).Clone();

            return clonedParms;
        }

        /// <summary>
        /// 为即将执行准备一个命令
        /// </summary>
        /// <param name="cmd">SqlCommand对象</param>
        /// <param name="conn">SqlConnection对象</param>
        /// <param name="trans">IDbTransaction对象</param>
        /// <param name="cmdType">执行命令的类型（存储过程或T-SQL，等等）</param>
        /// <param name="cmdText">存储过程名称或者T-SQL命令行, e.g. Select * from Products</param>
        /// <param name="cmdParms">SqlParameters to use in the command</param>
        private static void PrepareCommand(IDbCommand cmd, IDbConnection conn, IDbTransaction trans, CommandType cmdType, string cmdText, IDbDataParameter[] cmdParms)
        {
            if (conn.State != ConnectionState.Open)
                conn.Open();

            cmd.Connection = conn;
            cmd.CommandText = cmdText;

            if (trans != null)
                cmd.Transaction = trans;

            cmd.CommandType = cmdType;

            if (cmdParms != null)
            {
                foreach (IDbDataParameter parm in cmdParms)
                    cmd.Parameters.Add(parm);
            }
        }

        /// <summary>
        /// 根据传入的Key获取配置文件中
        /// 相应Key的数据库连接字符串
        /// </summary>
        /// <param name="Key"></param>
        /// <returns></returns>
        public static string GetConnectionString(string Key)
        {
            try
            {
                return CommonUtils.GetConfigValueByKey(Key);
            }
            catch
            {
                throw new Exception("web.config文件appSettings中数据库连接字符串未配置或配置错误，必须为Key=\"connectionString\"");
            }
        }      

        /// <summary>
        /// 用于数据库类型的字符串枚举转换
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="value"></param>
        /// <returns></returns>
        public static T DatabaseTypeEnumParse<T>(string value)
        {
            try
            {
                return CommonUtils.EnumParse<T>(value);
            }
            catch
            {
                throw new Exception("数据库类型\"" + value + "\"错误，请检查！");
            }
        }                             
    }

 public class DbFactory
    {
        /// <summary>
        /// 根据配置文件中所配置的数据库类型
        /// 来获取命令参数中的参数符号oracle为":",sqlserver为"@"
        /// </summary>
        /// <returns></returns>
        public static string CreateDbParmCharacter()
        {
            string character = string.Empty;

            switch (DBHelper.DbType)
            {
                case DatabaseType.SQLSERVER:
                    character = "@";
                    break;
                case DatabaseType.ORACLE:
                    character = ":";
                    break;
                case DatabaseType.ACCESS:
                    character = "@";
                    break;
                default:
                    throw new Exception("数据库类型目前不支持！");
            }

            return character;
        }

        /// <summary>
        /// 根据配置文件中所配置的数据库类型和传入的
        /// 数据库链接字符串来创建相应数据库连接对象
        /// </summary>
        /// <param name="connectionString"></param>
        /// <returns></returns>
        public static IDbConnection CreateDbConnection(string connectionString)
        {
            IDbConnection conn = null;
            switch (DBHelper.DbType)
            {
                case DatabaseType.SQLSERVER:
                    conn = new SqlConnection(connectionString);
                    break;
                case DatabaseType.ORACLE:
                    conn = new OracleConnection(connectionString);
                    break;
                case DatabaseType.ACCESS:
                    conn = new OleDbConnection(connectionString);
                    break;
                default:
                    throw new Exception("数据库类型目前不支持！");
            }

            return conn;
        }

        /// <summary>
        /// 根据配置文件中所配置的数据库类型
        /// 来创建相应数据库命令对象
        /// </summary>
        /// <returns></returns>
        public static IDbCommand CreateDbCommand()
        {
            IDbCommand cmd = null;
            switch (DBHelper.DbType)
            {
                case DatabaseType.SQLSERVER:
                    cmd = new SqlCommand();
                    break;
                case DatabaseType.ORACLE:
                    cmd = new OracleCommand();
                    break;
                case DatabaseType.ACCESS:
                    cmd = new OleDbCommand();
                    break;
                default:
                    throw new Exception("数据库类型目前不支持！");
            }

            return cmd;
        }

        /// <summary>
        /// 根据配置文件中所配置的数据库类型
        /// 来创建相应数据库适配器对象
        /// </summary>
        /// <returns></returns>
        public static IDbDataAdapter CreateDataAdapter()
        {
            IDbDataAdapter adapter = null;
            switch (DBHelper.DbType)
            {
                case DatabaseType.SQLSERVER:
                    adapter = new SqlDataAdapter();
                    break;
                case DatabaseType.ORACLE:
                    adapter = new OracleDataAdapter();
                    break;
                case DatabaseType.ACCESS:
                    adapter = new OleDbDataAdapter();
                    break;
                default:
                    throw new Exception("数据库类型目前不支持！");
            }

            return adapter;
        }

        /// <summary>
        /// 根据配置文件中所配置的数据库类型
        /// 和传入的命令对象来创建相应数据库适配器对象
        /// </summary>
        /// <returns></returns>
        public static IDbDataAdapter CreateDataAdapter(IDbCommand cmd)
        {
            IDbDataAdapter adapter = null;
            switch (DBHelper.DbType)
            {
                case DatabaseType.SQLSERVER:
                    adapter = new SqlDataAdapter((SqlCommand)cmd);
                    break;
                case DatabaseType.ORACLE:
                    adapter = new OracleDataAdapter((OracleCommand)cmd);
                    break;
                case DatabaseType.ACCESS:
                    adapter = new OleDbDataAdapter((OleDbCommand)cmd);
                    break;
                default: throw new Exception("数据库类型目前不支持！");
            }

            return adapter;
        }

        /// <summary>
        /// 根据配置文件中所配置的数据库类型
        /// 来创建相应数据库的参数对象
        /// </summary>
        /// <returns></returns>
        public static IDbDataParameter CreateDbParameter()
        {
            IDbDataParameter param = null;
            switch (DBHelper.DbType)
            {
                case DatabaseType.SQLSERVER:
                    param = new SqlParameter();
                    break;
                case DatabaseType.ORACLE:
                    param = new OracleParameter();
                    break;
                case DatabaseType.ACCESS:
                    param = new OleDbParameter();
                    break;
                default:
                    throw new Exception("数据库类型目前不支持！");
            }

            return param;
        }

        /// <summary>
        /// 根据配置文件中所配置的数据库类型
        /// 和传入的参数来创建相应数据库的参数数组对象
        /// </summary>
        /// <returns></returns>
        public static IDbDataParameter[] CreateDbParameters(int size)
        {
            int i = 0;
            IDbDataParameter[] param = null;
            switch (DBHelper.DbType)
            {
                case DatabaseType.SQLSERVER:
                    param = new SqlParameter[size];
                    while (i < size) { param[i] = new SqlParameter(); i++; }
                    break;
                case DatabaseType.ORACLE:
                    param = new OracleParameter[size];
                    while (i < size) { param[i] = new OracleParameter(); i++; }
                    break;
                case DatabaseType.ACCESS:
                    param = new OleDbParameter[size];
                    while (i < size) { param[i] = new OleDbParameter(); i++; }
                    break;
                default:
                    throw new Exception("数据库类型目前不支持！");

            }

            return param;
        }

        /// <summary>
        /// 根据配置文件中所配置的数据库类型
        /// 来创建相应数据库的事物对象
        /// </summary>
        /// <returns></returns>
        public static IDbTransaction CreateDbTransaction()
        {
            IDbConnection conn = CreateDbConnection(DBHelper.ConnectionString);

            if (conn.State == ConnectionState.Closed)
            {
                conn.Open();
            }

            return conn.BeginTransaction();
        }
    }

/// <summary>
    /// 数据库类型枚举，需要扩展类型可在此添加
    /// </summary>
    public enum DatabaseType
    {
        SQLSERVER,
        ORACLE,
        ACCESS,
        MYSQL
    }

Method 2.

First of all,create a abstract ADO.NET Helper,with the function the same as the above-mentioned DBHelper.But it is abstract with the abstract method,for example, protected abstract IDbConnection CreateDbConnection();protected abstract IDbCommand CreateDbCommand(string commandText, IDbConnection con);protected abstract IDbDataAdapter CreateDbDataAdapter(IDbCommand cmd);

Then create the concrete some DBHelper,for instance,SQLDBHelper.The results are as follows.

 public class SQLDBHelper: AbstractDBHelper
    { 
        internal override IDbConnection CreateDbConnection()
        {
            return new SqlConnection(_connectionString);
        } 
        protected override IDbCommand CreateDbCommand(string commandText, IDbConnection con)
        {
            return new SqlCommand(commandText, (SqlConnection)con);
        }
        
        ......................... 
    }