Question

MSDN包含this code example：

// This function takes arguments for 2 connection strings and commands to create a transaction 
// involving two SQL Servers. It returns a value > 0 if the transaction is committed, 0 if the 
// transaction is rolled back. To test this code, you can connect to two different databases 
// on the same server by altering the connection string, or to another 3rd party RDBMS by 
// altering the code in the connection2 code block.
static public int CreateTransactionScope(
    string connectString1, string connectString2,
    string commandText1, string commandText2)
{
    // Initialize the return value to zero and create a StringWriter to display results.
    int returnValue = 0;
    System.IO.StringWriter writer = new System.IO.StringWriter();

    try
    {
        // Create the TransactionScope to execute the commands, guaranteeing
        // that both commands can commit or roll back as a single unit of work.
        using (TransactionScope scope = new TransactionScope())
        {
            using (SqlConnection connection1 = new SqlConnection(connectString1))
            {
                // Opening the connection automatically enlists it in the 
                // TransactionScope as a lightweight transaction.
                connection1.Open();

                // Create the SqlCommand object and execute the first command.
                SqlCommand command1 = new SqlCommand(commandText1, connection1);
                returnValue = command1.ExecuteNonQuery();
                writer.WriteLine("Rows to be affected by command1: {0}", returnValue);

                // If you get here, this means that command1 succeeded. By nesting
                // the using block for connection2 inside that of connection1, you
                // conserve server and network resources as connection2 is opened
                // only when there is a chance that the transaction can commit.   
                using (SqlConnection connection2 = new SqlConnection(connectString2))
                {
                    // The transaction is escalated to a full distributed
                    // transaction when connection2 is opened.
                    connection2.Open();

                    // Execute the second command in the second database.
                    returnValue = 0;
                    SqlCommand command2 = new SqlCommand(commandText2, connection2);
                    returnValue = command2.ExecuteNonQuery();
                    writer.WriteLine("Rows to be affected by command2: {0}", returnValue);
                }
            }

            // The Complete method commits the transaction. If an exception has been thrown,
            // Complete is not  called and the transaction is rolled back.
            scope.Complete();

        }

    }
    catch (TransactionAbortedException ex)
    {
        writer.WriteLine("TransactionAbortedException Message: {0}", ex.Message);
    }
    catch (ApplicationException ex)
    {
        writer.WriteLine("ApplicationException Message: {0}", ex.Message);
    }

    // Display messages.
    Console.WriteLine(writer.ToString());

    return returnValue;
}

我不清楚：

我什么时候需要捕获TransactionAbortedException？
我目前正在应用程序生存期内存储与数据库的连接，而不是每次都打开和关闭它。这与使用交易有冲突吗？（或者这是一般的缺陷吗？）
如果我不关心值是否实际插入，我需要做什么？（我只是想确保数据库不会被破坏。）

Answer 1

不，TransactionScope不需要try / catch，因为您应该已经通过using使用它了，最后一步（根据示例）应该标记它已完成。如果它在没有的情况下点击Dispose() ，则会回滚。

你的子弹：

你没有，除非你有非常具体的理由来处理这个例外;我从来没有必要以特定的方式处理这种情况 - 它是如此出乎意料，我很高兴它成为一个真正的特殊事件。

存储您自己的开放连接在这里不是一个好主意 - 除了潜在的线程问题，以及不必要的开放连接：您忽略了内置已经连接池的事实默认情况下（至少使用SQL Server）。含义：您根据需要创建/打开新的SqlConnection（严格限制范围），并且池担心实际连接 - 您可能在此处添加开销，但获得的很少（在池中找到现有连接非常快）。如果仔细检查，您可能会注意到即使您Close()连接，db-server也会报告它正在使用中;那是因为你的Close()只是把它放回池中重复使用

没什么;交易应该是ACID

Answer 2

永远保持开放连接并不是一个好习惯。如果您正在处理Web应用程序，那么您将轻松达到最大连接数。最好始终保持连接实例并打开连接执行db操作然后关闭连接。

使用Using（）{}是处理数据库组件的正确方法。

我需要通过try / catch包装TransactionScope吗？

2 个答案: