Session instead of viewsate

Question

I have found many questions here about storing values in viewstate, but haven't found a good answer.

I have a situation when i retrieve large amount of data from database. Then i filter and manipulate the data according to my needs (so it is a preety heavy process). Then I put the result inside a list of custom class. For example lets say this class will be Person

List<Person> persons = new List<Person>();

private void FillPersons()
{
   //Call to webservice
   persons = ws.GetPersonsList();

   //Do all kind of custom filtering

   //Manipulate the data

}

Now the whole FillPersons() method is a heavy process that returns pretty small amount of data. And unfortunately it can't be moved to SQL and the heaviness is in the process, but that is not the point.

The point is that i need to reuse this data on the page between post backs. Right now in order to spare the additional call to FillPersons() I mark Person class as serializeable and store the list in the viewstate, that works fine except the fact that the page becomes 1mb size because of the viewstate. According to what i have read, it is not so acceptable approach i.e. it is not secure and it blows the source code making the page heavy etc. (second is what most concerns me)

So it leaves me with a session. However session is persisted not only between postbacks, but much after it, even when user leaves the page. Or worst- the session will end before user decide to postback. So finding the best time span for session lifetime is mission impossible.

My question is what is the best practice to reuse "datasets" between postbacks? What you guys do in such cases?

Thanks.

PS: hidden fields etc. is not an option.

Answer 1

You can store this kind of data in the Cache. It is application wide, so depending on what you add use the key accordingly.

var key = UserID + "_personList";
Cache.Add(key, personList, null, 
  DateTime.Now.AddSeconds(60), 
  Cache.NoSlidingExpiration,
  CacheItemPriority.High, 
  null);

Note that you can never assume that the data is in the cache (it might have been flushed) so always check if it returns null and than refill it.