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    <p>If your page does not modify any session variables, you can opt out of most of this lock.</p> <pre><code>&lt;% @Page EnableSessionState="ReadOnly" %&gt; </code></pre> <p>If your page does not read any session variables, you can opt out of this lock entirely, for that page.</p> <pre><code>&lt;% @Page EnableSessionState="False" %&gt; </code></pre> <p>If none of your pages use session variables, just turn off session state in the web.config.</p> <pre><code>&lt;sessionState mode="Off" /&gt; </code></pre> <p>I'm curious, what do you think "a ThreadSafe collection" would do to become thread-safe, if it doesn't use locks?</p> <p>Edit: I should probably explain by what I mean by "opt out of most of this lock". Any number of read-only-session or no-session pages can be processed for a given session at the same time without blocking each other. However, a read-write-session page can't start processing until all read-only requests have completed, and while it is running it must have exclusive access to that user's session in order to maintain consistency. Locking on individual values wouldn't work, because what if one page changes a set of related values as a group? How would you ensure that other pages running at the same time would get a consistent view of the user's session variables?</p> <p>I would suggest that you try to minimize the modifying of session variables once they have been set, if possible. This would allow you to make the majority of your pages read-only-session pages, increasing the chance that multiple simultaneous requests from the same user would not block each other.</p>
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    1. POI just discovered why all ASP.Net websites are slow, and I am trying to work out what to do about it
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    1. USJoel Mueller
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    1. COHi Joel Thanks for your time on this answer. These are some good suggestions and some food for thought. I don't understand your reasoning for saying all values for a session must be exclusively locked across the whole request. ASP.Net Cache values can be altered at any time by any thread. Why should this be different for session? As an aside - one problem I have with the readonly option is that if a developer does add a value to the session when it is readonly mode, it silently fails (no exception). In fact it keeps the value for the rest of the request - but not beyond.
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    2. CO@James - I'm just guessing at the motivations of the designers here, but I imagine it's more common to have multiple values depend on each other in a single user's session than in a cache that can be purged for lack of use or low-memory reasons at any time. If one page sets 4 related session variables, and another reads them after only two have been modified, that could easily lead to some very difficult-to-diagnose bugs. I imagine the designers chose to view "the current state of a user's session" as a single unit for locking purposes for that reason.
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    3. COIn addition, keep in mind that when you're using StateServer or SQL Server session state providers, all session variables for a given user are serialized and shipped off to the server in a single binary blob, at the end of a request. Trying to synchronize individual variables within this blob, as they are changed in realtime, would be pretty terrible for performance. It would mean potentially dozens of calls to the server per request, instead of just one read and one write.
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

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