Question

Do I have to lock access to instance members?

Example:

public class HttpModule : IHttpModule
{
    //...

    Dictionary<int, int> foo;

    void UseFoo(int a, int b)
    {
        foo[a] = b;
    }
}

Answer 1

It’s not crystal clear to me so far from the MSDN documentation, but I found a forum post from someone who claims to know the answer. It sounds like you shouldn’t expect bad stuff to happen with your implementation, but you should be aware that foo‘s state will not necessarily be shared across all results since your HttpModule will be created once per HttpApplication that IIS chooses to keep in its pool.