【IT168技术文档】
刚下载了Microsoft.ApplicationBlocks.Data看了看，了解了Sqlhelper.ExecuteReader返回的datareader是如何关闭的。
首先在SqlHelper类中有个枚举类型的变量SqlConnectionOwnership，它有两个值Internal，External； 用来指示connection的关闭方式。当传给ExecuteReader的参数为External时（由外部调用者传入connection），connection由调用者关闭，否则cmd.ExecuteReader(CommandBehavior.CloseConnection),即在调用command的ExecuteReader时设置为关闭datareader的时候同时自动关闭connection.
相关代码如下：
/**//// <summary> /// This enum is used to indicate whether the connection was provided by the caller, or created by SqlHelper, so that /// we can set the appropriate CommandBehavior when calling ExecuteReader() /// </summary> private enum SqlConnectionOwnership { /**//// <summary>Connection is owned and managed by SqlHelper</summary> Internal, /**//// <summary>Connection is owned and managed by the caller</summary> External } /**/////////////////// private static SqlDataReader ExecuteReader(SqlConnection connection, SqlTransaction transaction, CommandType commandType, string commandText, SqlParameter[] commandParameters, SqlConnectionOwnership connectionOwnership) { if( connection == null ) throw new ArgumentNullException( "connection" ); bool mustCloseConnection = false; // Create a command and prepare it for execution SqlCommand cmd = new SqlCommand(); try { PrepareCommand(cmd, connection, transaction, commandType, commandText, commandParameters, out mustCloseConnection ); // Create a reader SqlDataReader dataReader; // Call ExecuteReader with the appropriate Command Behavior if (connectionOwnership == SqlConnectionOwnership.External) { dataReader = cmd.ExecuteReader(); } else { dataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection); } bool canClear = true; foreach(SqlParameter commandParameter in cmd.Parameters) { if (commandParameter.Direction != ParameterDirection.Input) canClear = false; } if (canClear) { cmd.Parameters.Clear(); } return dataReader; } catch { if( mustCloseConnection ) connection.Close(); throw; } }
