Question

I have a null check in code that is checking to see whether a cookie exists in the response object already:

         if (HttpContext.Current.Response.Cookies["CookieName"] != null)
        {
            sessionCookie = HttpContext.Current.Response.Cookies["CookieName"];
            cookieValue = sessionCookie.Value;
        }

When I check through the debugger the key doesn’t exist before the check, but it does exists after the check. Thus the return value from the cookie is null. Does checking for a cookies existence automatically create the cookie?

Thanks in advance

Answer 1

This happens because HttpContext.Current is associated with the thread that the request is currently executing on. On a different thread, the framework has no way to know which request you want to use.

There are ways to fix this– for example .NET’s BackgroundWorker can propagate context to another thread. The Asynchronous Pages support in ASP.NET will also propagate context correctly.

So you have two options: either rewrite all your async code to use context-passing async mechanisms like BackgroundWorker or Async Pages, or change your code to check for HttpContext.Current==null before trying to access any properties of HttpContext.Current