如何DataReader的工作？ [英] How DataReader works?

问题描述

我在想，SqlDataReader的不应该工作，如果没有对SQLServer的任何连接。

I was thinking that the SQLDataReader should not work if there is no connection to the SQLServer.

我尝试了这种情况。我执行的ExecuteReader然后停止SQLServer服务，并试图遍历DataReader的。我的预期是一个例外，但它给了后，其他的结果之一。理想情况下，DataReader的应读一行从数据流的时刻，被连接到数据库服务器并且如果我们断开DB服务器应该抛出一个异常？

I experimented this scenario. I execute the ExecuteReader then stop the SQLServer Service and tried to iterate through the DataReader. What I expected was an exception, but it gave the results one after the other. Ideally the DataReader should read one row at a time from the stream that gets connected to the DB server and which should throw an exception if we disconnect the DB server?

我不知道，这是什么，我在这里失踪。

I don't know, What is it that I am missing here.

推荐答案

我强烈怀疑，读者一次读入一批结果。这是一个很多比一行更有效的时间（考虑在单行只有几个字节的情况......你不希望每行的网络数据包时，它可以检索到大量的行中的单个数据包）。它也可能允许数据库早期释放其内部资源。 - 如果所述数据读取器读取了所有的结果（当只有几个），它可以有效地忘记有关查询

I strongly suspect that the reader reads a batch of results at a time. That's a lot more efficient than one row at a time (think about the situation where a single row is only a few bytes... you don't want a network packet per row when it could have retrieved lots of rows in a single packet). It also potentially allows the database to release its internal resources early - if the data reader has read all the results (when there are only a few) it can effectively forget about the query.

我想，如果你尝试与返回的大量结果的查询同类型的东西，你会得到预期的异常。

I suspect if you try the same type of thing with a query returning lots of results, you'd get the expected exception.

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