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Tom
Tom

Reputation: 6707

creating expiring ASP.NET session value

I like to create a session value that expires in 5 minutes.

How to do that, do I need to manually compare creation time when I read it?

Session("sessionval") = myvariable
Session("sessioncreated") = now

Upvotes: 5

Views: 3972

Answers (7)

Alex from Jitbit
Alex from Jitbit

Reputation: 60672

Sorry to resurrect an old question, but I faced exactly the same problem and had to create an extension-class for the HttpSession object.

Here's my blog article on this

PS. the code:

public static class SessionExtender
{
    public static void AddWithTimeout(this HttpSessionState session,
        string name,
        object value,
        TimeSpan expireAfter)
    {
        session[name] = value;
        session[name + "ExpDate"] = DateTime.Now.Add(expireAfter);
    }

    public static object GetWithTimeout(
        this HttpSessionState session,
        string name)
    {
        object value = session[name];
        if (value == null) return null;

        DateTime? expDate = session[name + "ExpDate"] as DateTime?;
        if (expDate == null) return null;

        if (expDate < DateTime.Now)
        {
            session.Remove(name);
            session.Remove(name + "ExpDate");
            return null;
        }

        return value;
    }
}

Upvotes: 2

JoshBerke
JoshBerke

Reputation: 67078

If you want to use the SessionState you could create your own wrapper so instead of caching the actual item, you can cache the wrapper. Here is a quick dirty untested example of a wrapper that checks if the item is null, or if it has expired it will call a Func that you can provide a refreshed item.

The Func takes the last set value so if you can determine if the value is still valid you could avoid reloading it.

public class TimeExpirationItem<T>
{
    private T _item=default(T);
    private TimeSpan _expirationDuration;
    private Func<T> _getItemFunc;
    private DateTime _expiresTime;
    public TimeExpirationItem(TimeSpan expirationDuration, Func<T, T> getItemFunc)
    {
        this._getItemFunc = getItemFunc;
        this._expirationDuration = expirationDuration;
    }
    public T Item
    {
        get
        {
            if (_item == null || ItemIsExpired())
            {
                _item = _getItemFunc(_item);
                _expiresTime = DateTime.Now.Add(_expirationDuration);
            }
            return _item;
        }
    }
    public bool ItemIsExpired()
    {
        return DateTime.Now > _expiresTime;
    }
}

Again this code is provided as is with no warranty and it is untested but is an example of the things you can do.

Using it would be something like the following:

Session.Add("ObjectKey",new TimeExpirationItem<MyObject>(new TimeSpan(0,0,5),mo=>MyObjectRepository.GetItemByLogin(Request.User.Identity.Name));

Upvotes: 3

Cerebrus
Cerebrus

Reputation: 25775

I tend to agree with TheTXI.

Although a single Session item cannot be assigned a custom timeout, you should note that in InProc session mode, Sessionstate is itself added as an item to the ASP.NET cache. This enables it to have a "timeout".

In your particular scenario, a Cache object is the best suited solution.

Upvotes: 1

NileshChauhan
NileshChauhan

Reputation: 5569

1) Put this in web.config

<configuration>
   <system.web>
     <sessionState mode="InProc" timeout="5">
     </sessionState>
   </system.web> 
</configuration>

2) Set System.Web.SessionState.HttpSessionState.Timeout = 5 mins.

Upvotes: -1

TheTXI
TheTXI

Reputation: 37895

If you are asking how to do it on a single variable I do not think it is possible, but you can define the session timeout period using the web.config

<system.web>  
    <sessionState timeout="5" />
<system.web>

this would affect all of your session objects, not just a single one.

My suggestion for giving a custom expiration date to a single item is to create a cookie, that way you can actually set it's expiration value.

Response.Cookies.Add(New Web.HttpCookie("AdminID", admin.AdminID))
Response.Cookies("AdminID").Expires = Now.AddMinutes(5)

Upvotes: 6

John Saunders
John Saunders

Reputation: 161783

That is correct. Session state doesn't have an Expiration concept.

If your data are not per-user, you can use Cache instead. You could even use Cache, but include the user name as part of the key, which would sort of give you an expiring session state.

Upvotes: 2

Canavar
Canavar

Reputation: 48088

you can not define custom timeout to a session variable.

Maybe you can use cache for this, with a unique key dependent to session.

You can set timeout to a cached item.

Cache.Insert("key_dependent_to_session", value, Nothing, 
  DateTime.Now.AddMinutes(5), TimeSpan.Zero)

Upvotes: 4

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