/// <summary>
/// Create and prepare a IDbCommand, and call ExecuteReader with the appropriate CommandBehavior.
/// </summary>
/// <remarks>
/// If we created and opened the connection, we want the connection to be closed when the DataReader is closed.
///
/// If the caller provided the connection, we want to leave it to them to manage.
/// </remarks>
/// <param name="connection">a valid IDbConnection, on which to execute this command</param>
/// <param name="transaction">a valid IDbTransaction, or 'null'</param>
/// <param name="commandType">the CommandType (stored procedure, text, etc.)</param>
/// <param name="commandText">the stored procedure name or T-SQL command</param>
/// <param name="commandParameters">an array of IDataParameters to be associated with the command or 'null' if no parameters are required</param>
/// <param name="connectionOwnership">indicates whether the connection parameter was provided by the caller, or created by DbHelper</param>
/// <returns>IDataReader containing the results of the command</returns>
private static IDataReader ExecuteReader(IDbConnection connection, IDbTransaction transaction, CommandType commandType, string commandText, IDataParameter[] commandParameters, IDbConnectionOwnership connectionOwnership)
{
//create a command and prepare it for execution
IDbCommand cmd = connection.CreateCommand();
PrepareCommand(cmd, connection, transaction, commandType, commandText, commandParameters);
//create a reader
IDataReader dr;
// call ExecuteReader with the appropriate CommandBehavior
if (connectionOwnership == IDbConnectionOwnership.External) {
dr = cmd.ExecuteReader();
}
else {
dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
}
// detach the IDataParameters from the command object, so they can be used again.
cmd.Parameters.Clear();
return dr;
}
/// <summary>
/// 执行指定数据库连接对象的数据阅读器.
/// </summary>
/// <remarks>
/// 如果是BaseDbHelper打开连接,当连接关闭DataReader也将关闭.
/// 如果是调用都打开连接,DataReader由调用都管理.
/// </remarks>
/// <param name="connection">一个有效的数据库连接对象</param>
/// <param name="transaction">一个有效的事务,或者为 'null'</param>
/// <param name="commandType">命令类型 (存储过程,命令文本或其它)</param>
/// <param name="commandText">存储过程名或SQL语句</param>
/// <param name="commandParameters">IDataParameters参数数组,如果没有参数则为'null'</param>
/// <param name="connectionOwnership">标识数据库连接对象是由调用者提供还是由BaseDbHelper提供</param>
/// <returns>返回包含结果集的IDataReader</returns>
private static IDataReader ExecuteReader(IDbConnection connection, IDbTransaction transaction, CommandType commandType, string commandText, IDataParameter[] commandParameters, IDbConnectionOwnership connectionOwnership)
{
if (connection == null) throw new ArgumentNullException("connection");
bool mustCloseConnection = false;
// 创建命令
IDbCommand cmd = Factory.CreateCommand();
try
{
PrepareCommand(cmd, connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection);
// 创建数据阅读器
IDataReader dataReader;
if (connectionOwnership == IDbConnectionOwnership.External)
{
dataReader = cmd.ExecuteReader();
}
else
{
dataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection);
}
m_querycount++;
// 清除参数,以便再次使用..
// HACK: There is a problem here, the output parameter values are fletched
// when the reader is closed, so if the parameters are detached from the command
// then the SqlReader can磘 set its values.
// When this happen, the parameters can磘 be used again in other command.
bool canClear = true;
foreach (IDataParameter commandParameter in cmd.Parameters)
{
if (commandParameter.Direction != ParameterDirection.Input)
canClear = false;
}
if (canClear)
{
cmd.Dispose();
cmd.Parameters.Clear();
}
return dataReader;
}
catch
{
if (mustCloseConnection)
connection.Close();
throw;
}
}
