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How to get all active session from asp.net application

My purpose here is to make sure that all the logged in users should not get logged out if application pool stops or restarts.
One way is that i can use out prox sessions and directly store them in database but this is going to impact application performance so i dont want to do that.
Another way i found is that, i can register a "IRegisteredObject" implemented class object in hosting environment.
public class SessionTracker : IRegisteredObject
{
//I created this class as singleton and exposed GetInstance method
public void Stop(bool immediate)
{
//Here i want to get all the sessions and store them in database
}
}
Register it in global object
public class Global : System.Web.HttpApplication
{
protected void Application_Start(Object sender, EventArgs e)
{
HostingEnvironment.RegisterObject(SessionTracker.GetInstance());
}
}
I want to get all the active session of application so that i can store them in database at the time of application pool restarts or stops suddenly.
Now when my application starts, at that time i will load all the database stored session states again and all the session states will be valid.
Also i found that i can use Session start and Session end events and add sessions in a list object. I am not sure how efficient it will be as it can take more memory in server side.
Please suggest a approach by which i can get all the sessions at once. Or Is it okay if i use session start and session end event of global.ascx.cs file? Is it going to impact memory utilization?

I did further investigation and created a POC to check if it creates copy of Sessions by reference or by value.
What i found is that it creates copy by reference. So technically there is no memory utilization issue if i add their reference in SessionTracker class. Here the complete implementation of SessionTracker class if somebody is interested to know about it
public class SessionTracker : IRegisteredObject
{
static readonly SessionTracker Tracker = new SessionTracker();
private static readonly Dictionary<string, HttpSessionState> _sessions = new Dictionary<string, HttpSessionState>();
private static readonly object padlock = new object();
private SessionTracker()
{
}
public void Stop(bool immediate)
{
try
{
//store them in database
}
catch (Exception ex)
{
throw;
}
}
public void AddSession(HttpSessionState session)
{
lock (padlock)
{
_sessions.Add(session.SessionID, session);
}
}
public void RemoveSession(HttpSessionState session)
{
lock (padlock)
{
_sessions.Remove(session.SessionID);
}
}
public static SessionTracker GetInstance()
{
return Tracker;
}
}

ASP.NET how to use Sessions, when and where to declare it?

I am trying to retrieve some data from db and store it some Session variable in order to have it in _Layout.cshtml on all pages, no matter what page the user will access from the start.
Global.asax:
protected void Application_Start()
{
...
Manager mng = new Manager();
HttpContext.Current.Session["company-cellphone"] = mng.GetContacts().CompanyCellphone;
}
Error: Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

you are trying to access the session from Application_Start but there is no live Session yet.
session is not available in all events of global.asax
as a workaround try this:
protected void Application_PreRequestHandlerExecute(object sender, EventArgs e)
{
if (Context.Handler is IRequiresSessionState || Context.Handler is IReadOnlySessionState)
{
HttpContext context = HttpContext.Current;
...
Manager mng = new Manager();
HttpContext.Current.Session["company-cellphone"] = mng.GetContacts().CompanyCellphone;
}
}
I'm not sure about your requirement but I would recommend to access the session in controller.initialize method
protected override void Initialize(System.Web.Routing.RequestContext requestContext)
{
base.Initialize(requestContext);
//// access session here
requestContext.HttpContext.Session["company-cellphone"]=mng.GetContacts().CompanyCellphone;
}

Application_Start runs before any sessions can be created. And a session is specific to a single client connecting to your application.
You can create a static class and store the company-cellphone value in it.
In your Models folder create a new class file named Global.cs in that file create a static class with properties that will hold your application level information.
public static class Global
{
static string companyCellPhone;
public static string companyCellPhone
{
get
{
return this.companyCellPhone;
}
set
{
this.companyCellPhone= value;
}
}
Then your Application_Start method would look something like this:
protected void Application_Start()
{
...
Manager mng = new Manager();
Global.companyCellPhone = mng.GetContacts().CompanyCellphone;
}

I'm going to go out on a limb and guess that this is a single global value to be viewed by all users. In that case you could store the value in HttpApplicationState rather than HttpSessionState:
public class Global : System.Web.HttpApplication
{
protected void Application_Start(object sender, EventArgs e)
{
Application["YourValue"] = "SomeValue";
}
}
I'm not necessarily advocating its use. But just as Session can store user-specific values, Application stores values that are global to the application.

Strange behavior of static variables in a web site

I prepared a very simple Web site to demonstrate this behavior.
It has one page with one Button and the following code:
public partial class TestStatic : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
Class1.SetValue();
Label1.Text = Class1.st.ToString();
}
}
protected void Button1_Click(object sender, EventArgs e)
{
Label1.Text = Class1.st.ToString();
}
}
and one class:
public class Class1
{
public Class1()
{
}
public static int st = 0;
public static void SetValue()
{
st = 1;
}
}
So when the page is loaded you see in Label1 that st=1. If user clicks on the Buttton that sometimes you can see st=0 and sometimes st=1. In debugging I see that sometimes command
public static int st = 0;
is executed when an user clicks on the Button and this is a reason why st is changed to zero. This behavior I can reproduce in framework 4.5 only: it does not occur in framework 3.5. Can somebody explain me such behavior?

Static data lives per application domain instance. Since the hosting (IIS) can unload application domains between web site calls, static data can be lost.
So, you really shouldn't rely on static in web apps.

static values are shared across all instances of a class inside of a single App Domain.
If you're using IIS Express, your appdomain may be getting recycled more often than you think it is.
reference this: Lifetime of ASP.NET Static Variable

Make available a variable in multiple forms in compact framework

I'm doing an application for a Windows CE 5.0 device that asks for the username in the first form (when the application is launched), and then I get the userId from a database table.
After that a menu form appears which receives the userId, and I have to send to each constructor of the menu options the userId in order to use it in those forms. I assume there must be a better way to do something like this.
Example:
public partial class Menu : Form
{
int userId;
public Menu(int userId)
{
InitializeComponent();
this.userId = userId;
}
private void buttonDelivery_Click(object sender, EventArgs e)
{
Delivery delivery = new Delivery(userId);
delivery.Show();
this.Hide();
}
...
May be I should use a global variable like this?
public static class UserConfiguration
{
public static int userId;
}
Isn't that also bad practice?
Finally bear in mind that compact framework doesn't support app.config files

Personally I'd vote for "neither", but would instead use some other architectural tools available.
I'd be highly inclined to have a class that incorporates all user info (the ID you're using and then maybe anything else, like name, etc). I'd create an instance and populate that info when the first Form (login) is submitted and I'd keep it in a DI container (I use this one specifically, but any CF-supporting container would work).
I'd then either use injection to either automatically push that instance into any class that needs it, or have the consumer pull it from the container as needed. Which mechanism I use would depend on which container I'm using and exactly how/when I need the info.
Since the data you're after is coming from a database, I'd actually be inclined to use an ORM (I use this one) to pull the data, which would give you the entity instance containing the user info you're after automatically anyway.

in my opinion both ways are good, in some cases some controls do not work properly if you change the constructor signature or in some cases your constructor would not be called if the framework always calls the one with no parameters. But really depends on the specific case.
I like more the method parameters way to pass the values, but the external class with static field would also work fine.
P.S. app.config is not the best place anyway to store runtime specific values so doesn't matter if supported or not by CF in this case ;-)

If you use a controller it can hold all the variables needed. The controller can have a static Instance property that instantiates itself (see Singleton object design pattern). When developing Mobile applications this is very common as memory is often a constraint. The rest of the methods are public members (not static) so you would access like this. You can either make them properties or just use the public member. Even with mobile we tend to not use properties as it just adds unecessary fluff and boxing/unboxing.
In one form you can use:
MainController.Instance.loginID = "me123";
on another you can use
MessageBox.Show("my loginID is: " + MainController.Instance.loginID);
You can also add methods like:
MainController.Instance.ClearSession();
Which internally just sets loginID to null. etc. Personally I use the main controller to show windows as well. Because in mobile we need to make sure our resources are cleaned up as well.
MainController.Instance.ShowLoginForm();
the MainController code as a start should look something like this:
public class MainController : IDisposable {
//all forms we are controlling
LoginForm _loginForm = null;
//all public members
public string loginID = null;
#region Singleton Instance stuff
private static MainController me = null;
private void MainController() { }
public static Instance {
get {
if(me == null) {
me = new MainController();
}
return me;
}
}
#endregion
//all public methods
public void Init(someargshere) {
//TODO some init like load config files, etc.
}
public void Dispose() {
//TODO cleanup
}
public void ClearSession() {
loginID = "";
}
public void ShowLoginForm() {
if(loginForm!=null) {
loginForm.Dispose();
loginForm == null;
}
loginForm = new LoginForm();
loginForm.Show();
loginForm.BringToFront();
}
//etc
}
So the very first thing you do in the Program.cs code is init your main controller
main(string[] args) {
//start a controller
MainController.Instance.Init(passomeargs if needed);
//now fire off our main form
Application.Run(new MainForm());
}
Now all forms there after can access it's data through the MainController
Personally I use commands and have the main controller hide and show forms based on the commands passed in so there is as little logic in the forms as possible. This may or may not lend well to what you are doing.
Good luck

Update UpdatePanel on different user’s web page

I have a web page (aspx). This page has a button , a UpdatePanel and a Timer. Now my problem is as follow suppose 10 users are on this page at the same time and suppose user number 3 and 8 click its button then all user’s UpdatePanel should get updated. What is right way to achieve this functionality?

Since each user is running its own copy of the web application so whats happenning on one user's browser can't be notified to the other user. One thing you could do is when one user clicks the button to update, you could save it, whereas all the user application could ping the server may be every 2 secs to know if updation happens and if so updates.

You could use a Global property. On that property, you can put an Observer pattern, and let the visitors subscribe. When you alter the Application property ( shared throughout all Sessions ), you call the Notify() method. The client Notify() method gets called, and there you put functionality to update the UpdatePanel.
This code is NOT TESTED, it is a guideline
// *** GLOBAL.ASAX
// This collection will contain all the updatepanels that need to be updated
private List<IUpdatePanelClient> _registeredClients = new List<IUpdatePanelClient>();
public static void RegisterClient(IUpdatePanelClient client)
{
_registeredClients.Add(client);
}
public static void UnregisterClient(IUpdatePanelClient client)
{
_registeredClients.Remove(client);
}
// Which client is triggering the update call ?
private IUpdatePanelClient _clientUpdating = null;
public static IUpdatePanelClient ClientUpdating
{
get { return _clientUpdating ; }
set { _clientUpdating = value; Notify(); }
}
// Notify the clients
public static void Notify()
{
foreach(IUpdatePanelClient client in _registeredClients)
{
client.Update();
}
}
// *** IUPdatePanelClient.CS
interface IUpdatePanelClient // Interface to make the calls
{
void Update();
}
// *** Your codepage
public class MyUpdatePanelPage : Page, IUpdatePanelClient // Inherit the interface
{
public void Page_Load(Object sender, EventArgs e)
{
MyUpdatePanelPage.Global.RegisterClient(this);
}
public void Btn_Click(Object sender, EventArgs e)
{
MyUpdatePanelPage.Global.ClientUpdating = this;
}
public void Update()
{
this._updatePanel1.Update();
}
}

Your question doesn't have enough information for anyone to answer properly. If there is information that you want to keep all users update-to-date on, store that information in a database. When one user edits the data from their user session, whenever other user's get their page refreshed, they will have the most updated data. If you want to have their page refreshed periodically, use a javascript timer.