Question

I have a function that assigns values to a dictionary created in c#.
After some computations in the function, the dictionary is compsed of a value and a key.
I need to create a session save this dictionary in this session.
Can anybody help?

Answer 1

Put simply, if you have a Dictionary<string, List<int>> then putting it in the session is not very complicated;

Dictionary<string, List<int>> myDict = new Dictionary<string, List<int>>();
HttpContext.Current.Session.Add("MyDictionary", myDict);

If you want to check if the Session already contains your dictionary, and only add it if it doesn’t then:

if(!HttpContext.Current.Session.ContainsKey("MyDictionary"))
{
    HttpContext.Current.Session.Add("MyDictionary", myDict);
}

To get it out, remember that it’s not typed, Session is effectively a dictionary of string, object so you’ll have to cast:

if(HttpContext.Current.Session.ContainsKey("MyDictionary"))
{
    Dictionary<string, List<int>> myDict = HttpContext.Current.Session["MyDictionary"] as Dictionary<string, List<int>>;
}

However, you should also consider what the lifecycle of this object is going to be – Session is not stable in that it has a finite lifetime – it will disappear after a predetermined time of inactivity, for example, so if you want it to hang around for a longer time then you may need to consider alternative strategies.

There’s a ton of documentation on Session over at MSDN and it’s also a very common topic on Stack Overflow.

Remember also that, as Session is effectively a Dictionary<String, Object> managed by the .Net Framework and IIS, you could also do:

Session["MyValues"] = new List<Int32>();

And, of course, on retrieval:

List<Int32> myValues = Session["MyValues"] as List<Int32>();

Other alternatives include the Cache; if your object is going to be available to all users of the application then this might be a better solution. Please see this answer for more information.

I’ve also voted to close your question as I believe it’s too localized, but I hope my answer helps you along the way.