We are running a very large web application in asp.net MVC .NET 4.0. Recently we had an audit done and the performance team says that there were a lot of null reference exceptions.

So I started investigating it from the dumps and event viewer. My understanding was as follows:

We are using Asyn Tasks in our controllers. We rely on HttpContext.Current.Items hashtable to store a lot of Application level values.

Task<Articles>.Factory.StartNew(() =>
        {
            System.Web.HttpContext.Current = ControllerContext.HttpContext.ApplicationInstance.Context;
            var service = new ArticlesService(page);
            return service.GetArticles();
        }).ContinueWith(t => SetResult(t, "articles"));

So we are copying the context object onto the new thread that is spawned from Task factory. This context.Items is used again in the thread wherever necessary. Say for ex:

public class SomeClass
  {
    internal static int StreamID
    {
        get
        {
            if (HttpContext.Current != null)
            {
                return (int)HttpContext.Current.Items["StreamID"];
            }
            else
            {
                return DEFAULT_STREAM_ID;
            }
        }
    }

This runs fine as long as number of parallel requests are optimal. My questions are as follows:

1. When the load is more and there are too many parallel requests, I notice that HttpContext.Current.Items is empty. I am not able to figure out a reason for this and this causes all the null reference exceptions.

2. How do we make sure it is not null ? Any workaround if present ?

NOTE: I read through in StackOverflow and people have questions like HttpContext.Current is null - but in my case it is not null and its empty. I was reading one more article where the author says that sometimes request object is terminated and it may cause problems since dispose is already called on objects. I am doing a copy of Context object - its just a shallow copy and not a deep copy.