支持多数据库访问组件

　　需求千变万化，我们的应用软件要满足支持多个数据库访问，应对以前的代码封闭不能改动。

  

一  定义数据库基础访问接口

/// <summary>
/// 数据库访问适配器
/// </summary>
public interface IDBAccessProvider
{

    /// <summary>
    /// 获取连接状态
    /// </summary>
    ConnectionState ConnState { get; }
    /// <summary>
    /// 是否存在一个已经开始的事务
    /// </summary>
    bool IsExistTrans { get; }

    /// <summary>
    /// 打开连接
    /// </summary>
    void OpenConn();
    /// <summary>
    /// 关闭连接
    /// </summary>
    void CloseConn();

    /// <summary>
    /// 开始事务
    /// </summary>
    void BeginTrans();
    /// <summary>
    /// 提交事务
    /// </summary>
    void CommitTrans();
    /// <summary>
    /// 回滚事务
    /// </summary>
    void RollbackTrans();

    /// <summary>
    /// 创建一个命令参数
    /// </summary>
    /// <param name="name">参数名称</param>
    /// <param name="value">参数值</param>
    /// <param name="dbType">参数类型</param>
    /// <param name="direction">参数方向</param>
    /// <returns>参数对象</returns>
    IDbDataParameter CreateParameter(string name, object value, DbType dbType, ParameterDirection direction);
    /// <summary>
    /// 创建一个命令参数
    /// </summary>
    /// <param name="name">参数名称</param>
    /// <param name="value">参数值</param>
    /// <param name="dbType">参数类型</param>
    /// <returns>参数对象</returns>
    IDbDataParameter CreateParameter(string name, object value, DbType dbType);
    /// <summary>
    /// 创建一个命令参数
    /// </summary>
    /// <param name="name">参数名称</param>
    /// <param name="value">参数值</param>
    /// <returns>参数对象</returns>
    IDbDataParameter CreateParameter(string name, object value);

    /// <summary>
    /// 执行一条Sql命令
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <param name="commandType">命令类型</param>
    void ExecuteNonQuery(string sqlText, List<IDbDataParameter> parames, CommandType commandType);
    /// <summary>
    /// 执行一条Sql命令
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    void ExecuteNonQuery(string sqlText, List<IDbDataParameter> parames);
    /// <summary>
    /// 执行一条Sql命令
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    void ExecuteNonQuery(string sqlText);

    /// <summary>
    /// 执行一条查询Sql命令,返回一个DataReader
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <param name="commandType">命令类型</param>
    /// <param name="behavior"></param>
    /// <returns></returns>
    IDataReader ExecuteReader(string sqlText, List<IDbDataParameter> parames, CommandType commandType, CommandBehavior behavior);
    /// <summary>
    /// 执行一条查询Sql命令,返回一个DataReader
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <param name="commandType">命令类型</param>
    /// <returns></returns>
    IDataReader ExecuteReader(string sqlText, List<IDbDataParameter> parames, CommandType commandType);
    /// <summary>
    /// 执行一条查询Sql命令,返回一个DataReader
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <returns></returns>
    IDataReader ExecuteReader(string sqlText, List<IDbDataParameter> parames);
    /// <summary>
    /// 执行一条查询Sql命令,返回一个DataReader
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <returns></returns>
    IDataReader ExecuteReader(string sqlText);

    /// <summary>
    /// 执行一条查询Sql命令,返回一个结果集的第一行第一列的值
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <param name="commandType">命令类型</param>
    /// <returns></returns>
    object ExecuteScalar(string sqlText, List<IDbDataParameter> parames, CommandType commandType);
    /// <summary>
    /// 执行一条查询Sql命令,返回一个结果集的第一行第一列的值
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <returns></returns>
    object ExecuteScalar(string sqlText, List<IDbDataParameter> parames);
    /// <summary>
    /// 执行一条查询Sql命令,返回一个结果集的第一行第一列的值
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <returns></returns>
    object ExecuteScalar(string sqlText);
}

二  数据库访问基类

/// <summary>
/// 数据库访问适配器基类
/// </summary>
internal abstract class DBAccessProviderBase : IDBAccessProvider
{
    private IDbConnection _conn;
    private IDbTransaction _trans;

    public DBAccessProviderBase(string connString)
    {
        _conn = CreateConnection();
        _conn.ConnectionString = connString;
    }

    /// <summary>
    /// 创建一个命令对象
    /// </summary>
    /// <returns></returns>
    protected abstract IDbCommand CreateCommand();
    /// <summary>
    /// 创建一个连接对象
    /// </summary>
    /// <returns></returns>
    protected abstract IDbConnection CreateConnection();


    /// <summary>
    /// 获取连接状态
    /// </summary>
    public ConnectionState ConnState { get { return _conn.State; } }
    /// <summary>
    /// 是否存在一个已经开始的事务
    /// </summary>
    public bool IsExistTrans { get { return _trans != null; } }

    /// <summary>
    /// 打开连接
    /// </summary>
    public void OpenConn() { _conn.Open(); }
    /// <summary>
    /// 关闭连接
    /// </summary>
    public void CloseConn() { _conn.Close(); }

    /// <summary>
    /// 开始事务
    /// </summary>
    public void BeginTrans()
    {
        _trans = _conn.BeginTransaction();
    }
    /// <summary>
    /// 提交事务
    /// </summary>
    public void CommitTrans()
    {
        if (_trans == null)
            throw new PSBaseException("没有开始任何事务.");
        _trans.Commit();
        _trans = null;
    }
    /// <summary>
    /// 回滚事务
    /// </summary>
    public void RollbackTrans()
    {
        if (_trans == null)
            throw new PSBaseException("没有开始任何事务.");
        _trans.Rollback();
        _trans = null;
    }

    /// <summary>
    /// 创建一个命令参数
    /// </summary>
    /// <param name="name">参数名称</param>
    /// <param name="value">参数值</param>
    /// <param name="dbType">参数类型</param>
    /// <param name="direction">参数方向</param>
    /// <returns>参数对象</returns>
    public IDbDataParameter CreateParameter(string name, object value, DbType dbType, ParameterDirection direction)
    {
        IDbCommand cmd = CreateCommand();
        IDbDataParameter result = cmd.CreateParameter();
        result.ParameterName = name;
        result.Direction = direction;
        result.DbType = dbType;
        result.Value = value;
        return result;
    }
    /// <summary>
    /// 创建一个命令参数
    /// </summary>
    /// <param name="name">参数名称</param>
    /// <param name="value">参数值</param>
    /// <param name="dbType">参数类型</param>
    /// <returns>参数对象</returns>
    public IDbDataParameter CreateParameter(string name, object value, DbType dbType)
    {
        IDbCommand cmd = CreateCommand();
        IDbDataParameter result = cmd.CreateParameter();
        result.ParameterName = name;
        result.DbType = dbType;
        result.Value = value;
        return result;
    }
    /// <summary>
    /// 创建一个命令参数
    /// </summary>
    /// <param name="name">参数名称</param>
    /// <param name="value">参数值</param>
    /// <returns>参数对象</returns>
    public IDbDataParameter CreateParameter(string name, object value)
    {
        IDbCommand cmd = CreateCommand();
        IDbDataParameter result = cmd.CreateParameter();
        result.ParameterName = name;
        result.Value = value;
        return result;
    }

    /// <summary>
    /// 执行一条Sql命令
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <param name="commandType">命令类型</param>
    public void ExecuteNonQuery(string sqlText, List<IDbDataParameter> parames, CommandType commandType)
    {
        IDbCommand cmd = CreateCommand();
        cmd.Connection = _conn;
        cmd.CommandText = sqlText;
        cmd.CommandType = commandType;
        if (parames != null)
            foreach (IDbDataParameter param in parames)
                cmd.Parameters.Add(param);
        if (_trans != null)
            cmd.Transaction = _trans;
        cmd.ExecuteNonQuery();
    }
    /// <summary>
    /// 执行一条Sql命令
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    public void ExecuteNonQuery(string sqlText, List<IDbDataParameter> parames)
    {
        ExecuteNonQuery(sqlText, parames, CommandType.Text);
    }
    /// <summary>
    /// 执行一条Sql命令
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    public void ExecuteNonQuery(string sqlText)
    {
        ExecuteNonQuery(sqlText, null, CommandType.Text);
    }

    /// <summary>
    /// 执行一条查询Sql命令,返回一个DataReader
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <param name="commandType">命令类型</param>
    /// <param name="behavior"></param>
    /// <returns></returns>
    public IDataReader ExecuteReader(string sqlText, List<IDbDataParameter> parames, CommandType commandType, CommandBehavior behavior)
    {
        IDbCommand cmd = CreateCommand();
        cmd.Connection = _conn;
        cmd.CommandText = sqlText;
        cmd.CommandType = commandType;
        if (parames != null)
            foreach (IDbDataParameter param in parames)
                cmd.Parameters.Add(param);
        if (_trans != null)
            cmd.Transaction = _trans;
        return cmd.ExecuteReader(behavior);
    }
    /// <summary>
    /// 执行一条查询Sql命令,返回一个DataReader
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <param name="commandType">命令类型</param>
    /// <returns></returns>
    public IDataReader ExecuteReader(string sqlText, List<IDbDataParameter> parames, CommandType commandType)
    {
        return ExecuteReader(sqlText, parames, commandType, CommandBehavior.Default);
    }
    /// <summary>
    /// 执行一条查询Sql命令,返回一个DataReader
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <returns></returns>
    public IDataReader ExecuteReader(string sqlText, List<IDbDataParameter> parames)
    {
        return ExecuteReader(sqlText, parames, CommandType.Text, CommandBehavior.Default);
    }
    /// <summary>
    /// 执行一条查询Sql命令,返回一个DataReader
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <returns></returns>
    public IDataReader ExecuteReader(string sqlText)
    {
        return ExecuteReader(sqlText, null, CommandType.Text, CommandBehavior.Default);
    }

    /// <summary>
    /// 执行一条查询Sql命令,返回一个结果集的第一行第一列的值
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <param name="commandType">命令类型</param>
    /// <returns></returns>
    public object ExecuteScalar(string sqlText, List<IDbDataParameter> parames, CommandType commandType)
    {
        IDbCommand cmd = CreateCommand();
        cmd.Connection = _conn;
        cmd.CommandText = sqlText;
        cmd.CommandType = commandType;
        if (parames != null)
            foreach (IDbDataParameter param in parames)
                cmd.Parameters.Add(param);
        if (_trans != null)
            cmd.Transaction = _trans;
        object result = cmd.ExecuteScalar();
        if (result == DBNull.Value)
            result = null;
        return result;
    }
    /// <summary>
    /// 执行一条查询Sql命令,返回一个结果集的第一行第一列的值
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <param name="parames">参数表</param>
    /// <returns></returns>
    public object ExecuteScalar(string sqlText, List<IDbDataParameter> parames)
    {
        return ExecuteScalar(sqlText, parames, CommandType.Text);
    }
    /// <summary>
    /// 执行一条查询Sql命令,返回一个结果集的第一行第一列的值
    /// </summary>
    /// <param name="sqlText">sql命令文本</param>
    /// <returns></returns>
    public object ExecuteScalar(string sqlText)
    {
        return ExecuteScalar(sqlText, null, CommandType.Text);
    }
}

三  SqlServer数据库

internal class MSSqlDBAccessProvider : DBAccessProviderBase
{
    public MSSqlDBAccessProvider(string connString) : base(connString) { }

    protected override IDbCommand CreateCommand()
    {
        return new SqlCommand();
    }

    protected override IDbConnection CreateConnection()
    {
        return new SqlConnection();
    }
}

 Oracle数据库：

internal class OracleClientDBAccessProvider : DBAccessProviderBase
{
    public OracleClientDBAccessProvider(string connString) : base(connString) { }

    protected override IDbCommand CreateCommand()
    {
        return new OracleCommand();
    }

    protected override IDbConnection CreateConnection()
    {
        return new OracleConnection();
    }
}

四  数据库访问适配器工厂类

/// <summary>
/// 数据库访问适配器工厂类
/// </summary>
public sealed class DBAccessProviderFactory
{
    /// <summary>
    /// 常数：Oracle.Data.OracleClient数据库驱动
    /// </summary>
    public const int PROVIDERTYPE_ORACLE_CLIENT = 1;
    /// <summary>
    /// 常数：Sql Server数据库驱动
    /// </summary>
    public const int PROVIDERTYPE_MSSQL = 2;

    /// <summary>
    /// 实例化适配器
    /// </summary>
    /// <param name="providerType">数据库驱动类型</param>
    /// <param name="connString">数据库连接字符串</param>
    /// <returns></returns>
    public static IDBAccessProvider GetDBAccessProvider(int providerType, string connString)
    {
        switch (providerType)
        {
            case PROVIDERTYPE_ORACLE_CLIENT:
                return new OracleClientDBAccessProvider(connString);
            case PROVIDERTYPE_MSSQL:
                return new MSSqlDBAccessProvider(connString);
        }
        throw new Exception("不支持的数据库类型.");
    }
}