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copied!<ol> <li>your code doesn't show where you open/close the connection; but the <em>reader</em> here will actually only be open <em>while you are iterating the data</em>. Deferred execution, etc. The only bit of your code that does this is the <code>.ToList()</code>, so it'll be fine. In the more general case, yes: the reader will be open for the amount of time you take to iterate it; if you do a <code>.ToList()</code> that will be minimal; if you do a <code>foreach</code> and (for every item) make an external http request and wait 20 seconds, then yes - it will be open for longer.</li> <li>Both have their uses; the non-buffered approach is great for huge results that you want to process as a stream, without ever having to load them into a single in-memory list (or even have all of them in memory at a time); returning a list keeps the connection closed quickly, and makes it easy to avoid accidentally using the connection while it already has an open reader, but is not ideal for large results</li> </ol> <p>If you return an iterator block, the caller can decide what is sane; if you always return a list, they don't have much option. A third way (that we do in dapper) is to make the choice theirs; we have an optional <code>bool</code> parameter which defaults to "return a list", but which the caller can change to indicate "return an iterator block"; basically:</p> <pre><code>bool buffered = true </code></pre> <p>in the parameters, and:</p> <pre><code>var data = QueryInternal<T>(...blah...); return buffered ? data.ToList() : data; </code></pre> <p>in the implementation. In most cases, returning a list is perfectly reasonable and avoids a lot of problems, hence we make that the default.</p>

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