Session is null when calling method from one controller to another...MVC

Question

I have an ASP.NET MVC app and i added a new controller to it and call a method from this new controller from an existing controller. I am using session variables and in controller A i call the method in controller B:

if (Session["Grid"] != null){}//session object is fine here
      ControllerB b  = new ControllerB ();
b.CallMethod();

In the new controller, which i'm calling B, the method looks like this:

public object CallMethod(){
    if (Session["Grid"] != null)//session object is null
        {
            //do my thing
        }
  }

The session variable isnt the problem, its the session object. Its completely null, hence my application blows up. The session is alive and well in controller A, so why is it null in controller B? Thank you

Solution 1

That's because ControllerB needs to initializes itself, and as part of this process it also sets Session, Request, Resposne etc accordingly.

So, you need to call the Initialize() method and pass it the current RequestContext. But, since it's marked as protected (because it wasn't meant to be called directly, only using the ControllerFactory), you'll have to expose it:

public class ControllerB : Controller
{
    public void InitializeController(RequestContext context)
    {
        base.Initialize(context);
    }
}

Then in your ControllerA:

var controllerB = new ControllerB();
controllerB.InitializeController(this.Request.RequestContext);

Alternatively, since the Session getter is actually a shorthand for this.ControllerContext.HttpContext.Session (same for Request, Response etc), you can set the ControllerContext instead:

var controllerB = new ControllerB();
controllerB.ControllerContext = new ControllerContext(this.Request.RequestContext, controllerB);

See MSDN

Solution 2

This is happening because Session is a property that is initialized different based on how the controller is called.

Instead of Session you can use HttpContext.Session. HttpContext refers to the current http request.

public object CallMethod(){
    if (HttpContext.Session["Grid"] != null)//session object is null
    {
        //do my thing
    }
}

Solution 3

This is easily fixed through the good coding practice of "tell, don't ask", ie you pass the required value into the method, rather than expecting it to go looking for it for itself:

if (Session["Grid"] != null)
{
    var b  = new ControllerB ();
    b.CallMethod(Session["Grid"]);
}

...
public object CallMethod(string grid)
{
    //do your thing
}

Comments

[BoundForGlory]

Hello haim770 - This is what i was looking for. Thank you very much

[Gokulan P H]

You saved my day :)