交易目的

本文关键字：交易 | 更新日期: 2023-09-27 18:31:29

我读了很多关于这个主题的文章，但我仍然有一些重要和基本的问题。如果不用于 SQL，事务的目的是什么？它在 WCF 中对我有什么帮助？本文展示了使用简单事务的示例：

http://msdn.microsoft.com/en-us/library/ms172152（v=vs.90）.aspx

如果下面的代码

不是为了回滚他们试图在代码失败时恢复的内容，那么下面的代码的目的是什么？

    void RootMethod()
{
     using(TransactionScope scope = new TransactionScope())
     {
          /* Perform transactional work here */
          SomeMethod();
          scope.Complete();
     }
}
void SomeMethod()
{
     using(TransactionScope scope = new TransactionScope())
     {
          /* Perform transactional work here */
          scope.Complete();
     }
}

交易目的

只有支持事务的资源才能参与事务。通常，这只是SQL Server。消息队列还支持事务。

如果您不使用任何启用事务的资源（如普通变量...），这将不会执行任何操作。

这里有

一个很好的例子

http://msdn.microsoft.com/en-us/library/system.transactions.transactionscope（v=vs.90）.aspx#Y500

在示例中（上面的链接，下面的代码），SQL 连接对象将自动参与事务 - 因此这些 SQL 命令不会在事务完成之前提交（scope.Complete）。 这样，只有当另一个发生时，才会在两个单独的服务器上发生这两个服务器。 任何异常都会导致两者回滚。

您的示例不清楚，因为它仅在该页面的上下文中描述嵌套范围。 该示例显示的内容将被视为嵌套，而不是一些可以执行任何有用操作的代码。

这是微软的示例代码，我认为它很清楚：

// 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;
}
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