Injecting the session into a wrapper class RSS

• • Reply
  

  mase

  Member

  54 Points

  65 Posts

  Injecting the session into a wrapper class

  Aug 13, 2010 05:39 PM|LINK

  I've seen how to Fake the SessionState object in MVC using Scott Hanselmans MvcMockHelpers, but I'm dealing with a separate problem.

  What I like to do is create a wrapper around the Session object to make objects a little more accessible and strongly typed rather than using keys all over. Here is basically what it does:

  public class SessionVars
  { 
      public SessionVars()
      {}
  
      public string CheckoutEmail
      {
          get { return Session[checkoutEmailKey] as string; }
          set { Session[checkoutEmailKey] = value; }
      }
  }
  

  So that I can just do this in my controllers and views:

  SessionVars s = new SessionVars();
  s.CheckoutEmail = "test@tester.com";
  

  Now the problem comes in when I want to write unit tests, this class is tightly coupled with the HttpSessionState. What I can't figure out is what is the right class to accept/pass so that I can pass in a FakeHttpSession into the SessionVars class. I've tried so many things with this, and this (below) will compile, but it can't cast the HttpSessionState into the IDictionary. I've tried ICollection, HttpSessionStateBase.

  public class SessionVars
  {
      public SessionVars() : this(HttpContext.Current.Session) { }
      public SessionVars(ICollection session)
      {
          Session = (IDictionary<string, object>)session;
      }
  
      public IDictionary<string, object> Session
      {
          get;
          private set;
      }
  
      public string CheckoutEmail
      {
          get { return Session[checkoutEmailKey] as string; }
          set { Session[checkoutEmailKey] = value; }
      }
  
      public Order Order
      {
          get { return Session[orderKey] as Order; }
          set { Session[orderKey] = value; }
      }
  }
  

  I'm missing something big here. I feel like this is possible and that I should even be that far off.

  Furthermore, I'm confused as to whether I should use the IHttpSessionState, HttpSessionStateBase or the HttpSessionStateWrapper. What is the abstract type that I'd use for the session object inside my SessionVars class? What is the type that I pass into the constructor? 

  dependency injection "ASP.NET MVC" unit testing ASP.NET

  * Mase *
• • Reply
  

  DigiMortal

  Contributor

  5728 Points

  954 Posts

  MVP

  Re: Injecting the session into a wrapper class

  Aug 13, 2010 07:22 PM|LINK

  In unit tests you should instantiate your session variables class like this:

  var myVarsCollection = new Dictionary<string,object>();
  myVarsCollection.Add("UserId", 1);
  myVarsCollection.Add("UserName", "ThisIsMe");
  ...
  
  
  var sessionVars = new SessionVars(myVarsCollection);

  
  myVarsCollection is your custom collection with faked session values. In your app code you use parameterless constructor. In tests you use constructor that takes dictionary with values you give. Just like code example I gave. This way you can avoid using all these session state classes in your tests.

  Don't forget to mark solution providing post as "Answered".
  
  Also visit my ASP.NET blog or follow me @ Twitter:twitter.com/gpeipman
• • Reply
  

  mase

  Member

  54 Points

  65 Posts

  Re: Injecting the session into a wrapper class

  Aug 13, 2010 09:04 PM|LINK

  Thanks for your response, but I think you may have misunderstood my question. The code I pasted builds, but doesn't run because it cannot cast the SessionState to an IDicitionary<string, object>.

  But I think I've solved my own problem and I'll post the code here shortly.

  * Mase *
• • Reply
  

  mase

  Member

  54 Points

  65 Posts

  Re: Injecting the session into a wrapper class

  Aug 13, 2010 09:09 PM|LINK

  So I figured it out, what my problem was that I had tried so many types for the constructor and abstract class, but I didn't take enough time to figure out why the one I thought should work didn't work. 

  Currently, HttpSessionState does not derive from HttpSessionStateBase. So you cannot simply cast from HttpSessionState to HttpSessionStateBase. So to handle this, Microsoft had introduced the HttpSessionStateWrapper to allow casting this way. BUT, you cannot cast the other way since the session may not always be available.

  Here is what I ended up figuring out:

  public SessionVars() : this( new HttpSessionStateWrapper(HttpContext.Current.Session) )
  { }
  
  
  public SessionVars(HttpSessionStateBase sessionWrapper)
  {
  	Session = sessionWrapper;
  }
  
  
  public HttpSessionStateBase Session
  {
  	get;
  	private set;
  }

  
  I can use the new HttpSessionStateWrapper(HttpContext.Current.Session) to cast the current session to the HttpSessionStateBase, which can be used to serve up fake sessions and real ones.

  * Mase *
  • Marked as answer by mase on Aug 13, 2010 09:10 PM