Is access to the Session thread-safe?

[Chris Newby]

When accessing, for example, an object stored in the session such as:

Session[ "MyObject" ].MyProperty = "Some Value";

Is access to MyObject thread-safe?

 

[Scott Allen]

Hi Chris:

Here are some details:

ASP.NET does manage access to session state with a ReaderWriterLock.
The default is to take a writer lock, which serializes requests coming
in on the same session (using EnableSessionState="ReadOnly" takes a
reader lock and does allow concurrent request processing on a
session).

In this example, you are not really modifying session state, but
modifying an object through a reference stored in session state. If
anyone else has a reference to the same object the code is only thread
safe if MyObject is thread safe.

Know what I mean?

 

[Chris Newby]

Yeah, makes perfect sense.

Could you possibly elaborate a little more on exactly when ASP.NET creates
and releases the ReaderWriter Lock?

Hi Chris:

Here are some details:

ASP.NET does manage access to session state with a ReaderWriterLock.
The default is to take a writer lock, which serializes requests coming
in on the same session (using EnableSessionState="ReadOnly" takes a
reader lock and does allow concurrent request processing on a
session).

In this example, you are not really modifying session state, but
modifying an object through a reference stored in session state. If
anyone else has a reference to the same object the code is only thread
safe if MyObject is thread safe.

Know what I mean?

--
Scott
http://www.OdeToCode.com/blogs/scott/

When accessing, for example, an object stored in the session such as:

Session[ "MyObject" ].MyProperty = "Some Value";

Is access to MyObject thread-safe?

 

[Scott Allen]

When the SessionStateModule catches the AcquireRequestState event
during request processing. This happens before control reaches the
ASPX page handler.

 

[Chris Newby]

Thanks Scott, very helpful//

When the SessionStateModule catches the AcquireRequestState event
during request processing. This happens before control reaches the
ASPX page handler.