Question

So here’s an excerpt from one of my classes:

    [ThreadStatic]
    readonly static private AccountManager _instance = new AccountManager();

    private AccountManager()
    {
    }

    static public AccountManager Instance
    {
        get { return _instance; }
    }

As you can see, it’s a singleton-per-thread – i.e. the instance is marked with the ThreadStatic attribute. The instance is also instantiated as part of static construction.

So that being the case, how is it possible that I’m getting a NullReferenceException in my ASP.NET MVC application when I try to use the Instance property?

Answer 1

Quoting MSDN ThreadStaticAttribute:

Do not specify initial values for
fields marked with
ThreadStaticAttribute, because such
initialization occurs only once, when
the class constructor executes, and
therefore affects only one thread. If
you do not specify an initial value,
you can rely on the field being
initialized to its default value if it
is a value type, or to a null
reference (Nothing in Visual Basic) if
it is a reference type.