HttpModule AcquireRequestState event handler has null sender

I have an HttpModule, something like this:

public class MyModule : IHttpModule
{
    public void Init(HttpApplication context)
    {
         context.AcquireRequestState += Context_OnAcquireRequestState;
    }

    private void Context_OnAcquireRequestState(object sender, EventArgs e)
    {
    HttpContext context = ((HttpApplication)sender).Context;
        ... etc
    }
}

I have noticed a problem occur开发者_StackOverflow中文版ring directly after the app pool is restarted, in which null is passed as the sender parameter of the AcquireRequestState event and I get a null reference exception. After some time the problem seems to resolve itself.

How could this be happening?

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HttpContext.Current should be set on the event handler thread by the infrastructure. Try using the static accessor instead of the sender on the event.