List all active ASP.NET Sessions

You can collect data about sessions in global.asax events Session_Start and Session_End (only in in-proc settings):

private static readonly List<string> _sessions = new List<string>();private static readonly object padlock = new object(); public static List<string> Sessions {       get       {            return _sessions;       }  }  protected void Session_Start(object sender, EventArgs e)  {      lock (padlock)      {          _sessions.Add(Session.SessionID);      }  }  protected void Session_End(object sender, EventArgs e)  {      lock (padlock)      {          _sessions.Remove(Session.SessionID);      }  }

You should consider use some of concurrent collections to lower the synchronization overhead. ConcurrentBag or ConcurrentDictionary. Or ImmutableList

https://msdn.microsoft.com/en-us/library/dd997373(v=vs.110).aspx

https://msdn.microsoft.com/en-us/library/dn467185.aspx

It does not seems right that there is not any class or method that provides this information. I think, it is a nice to have feature for SessionStateStoreProvider, to have a method which returns current active session, so that we don't have to actively track session life in session_start and session_end as mention by Jan Remunda.

Since I could not find any out of box method to get all session list, And I did not wanted to track session life as mentioned by Jan, I end up with this solution, which worked in my case.

public static IEnumerable<SessionStateItemCollection> GetActiveSessions(){    object obj = typeof(HttpRuntime).GetProperty("CacheInternal", BindingFlags.NonPublic | BindingFlags.Static).GetValue(null, null);    object[] obj2 = (object[])obj.GetType().GetField("_caches", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(obj);    for (int i = 0; i < obj2.Length; i++)    {        Hashtable c2 = (Hashtable)obj2[i].GetType().GetField("_entries", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(obj2[i]);        foreach (DictionaryEntry entry in c2)        {            object o1 = entry.Value.GetType().GetProperty("Value", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(entry.Value, null);            if (o1.GetType().ToString() == "System.Web.SessionState.InProcSessionState")            {                SessionStateItemCollection sess = (SessionStateItemCollection)o1.GetType().GetField("_sessionItems", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(o1);                if (sess != null)                {                    yield return sess;                }            }        }    }}

http://weblogs.asp.net/imranbaloch/archive/2010/04/05/reading-all-users-session.aspx

How this works :

InProc session data is stored in the HttpRuntime’s internal cache in an implementation of ISessionStateItemCollection that implements ICollection. In this code, first of all i got CacheInternal Static Property of HttpRuntime class and then with the help of this object i got _entries private member which is of type ICollection. Then simply enumerate this dictionary and only take object of type System.Web.SessionState.InProcSessionState and finaly got SessionStateItemCollection for each user.

Summary :

In this article, I show you how you can get all current user Sessions. However one thing you will find when executing this code is that it will not show the current user Session which is set in the current request context because Session will be saved after all the Page Events...