Few questions on WCF sessions

Found few interview questions on WCF session, Can anyone help me a开发者_如何学运维nswer these. I have gine through the msdn documentation for WCF, but still im not (100%) sure about answer to these questions

· Why we need the sessions? · Where session stores the session information? What is the general store for the WCF session?

· What is it a correlation? What parameters are mandatory for the correlation? · What order are the delivered messages processed in during the session? · Does the SessionMode.NotAllowed increase the performance?

· How does a client start a session?

Thanks.

Why use sessions? Only if you need to persist data between calls, or for some reason need to tie a client to a particular service instance (which is usually not a good idea).

In general, it's advised to think long and hard about your service before deciding to use sessions and durable sessions since doing so can have a big impact on performance. Many times there are better ways to solve problems.

Here's an article all about instance management in WCF (link). Hopefully it will answer most of your questions.

I strongly suggest reading chapter 4 in Juval Lowy's Programming WCF Services (link) for more information - that chapter goes into great detail on instance management and should answer all of your questions.