Question

从Oracle DB获取内容时遇到错误。

这是我的代码：

public virtual IDataReader LoadDataReaderWithSqlString(string strQuery, ISessionScope session)
    {
        var s = GetSession(session);
        using (var connection = s.Connection)
        {
            var command = connection.CreateCommand();
            command.Connection = connection;
            if (connection.State == ConnectionState.Closed || connection.State == ConnectionState.Broken)
                connection.Open();
            command.CommandType = CommandType.Text;
            command.CommandText = s.CreateSQLQuery(strQuery).ToString();
            s.Transaction.Enlist(command); // Set the command to exeute using the NHibernate's transaction
            using (var dataReader = command.ExecuteReader())
            {
                if(dataReader.Read())
                    return dataReader;
            }
        }
        return null;
    }

当我调试时，我能够在dataReader中看到返回值。我使用NHibernate来运行Raw SQL。我想返回DataReader。有人可以帮我吗？

Answer 1

您是否正在尝试返回已打开的IDataReader？问题是您将ExecuteReader包裹在using语句中。 using表示在执行dataReader内的代码后，您的using将被处理掉。所以你返回处置对象。解决方案是：删除using：

var dataReader = command.ExecuteReader();
if(dataReader.Read())
    return dataReader;

对于连接对象也一样。

添加

正如David在评论中提到的那样，您可能希望避免资源泄漏（我的意思是在打开连接但未执行命令的情况下），那么您应该处理这样的异常：

public virtual IDataReader LoadDataReaderWithSqlString(string strQuery, ISessionScope session) { try { var s = GetSession(session); var connection = s.Connection; var command = connection.CreateCommand(); command.Connection = connection; if (connection.State == ConnectionState.Closed || connection.State == ConnectionState.Broken) connection.Open(); command.CommandType = CommandType.Text; command.CommandText = s.CreateSQLQuery(strQuery).ToString(); s.Transaction.Enlist(command); // Set the command to exeute using the NHibernate's transaction try { var dataReader = command.ExecuteReader(); if(dataReader.Read()) return dataReader; } catch (DbException) { // error executing command connection.Close(); return null; // or throw; // it depends on your logic } } catch (DbException) { // if connection was not opened return null; // or throw; // it depends on your logic } return null; }

Answer 2

那是因为你有

using (var connection = s.Connection)和using (var dataReader = command.ExecuteReader())

using阻止将处置对象（此处connection和dataReader）

如果您需要返回dataReader

，请删除使用块

OracleDataReader。错误：操作无效。连接已关闭

2 个答案: