Application_Start versus OnInit versus constructor
app-startup, asp.net, httpapplication, lifecycle
Solution
Calling Application_Start the first time an instance of HttpApplication is created, but not on subsequent instances seems a bit of a hack. Perhaps Microsoft didn't want to explain the concept of a static constructor to people who didn't really want to know.
Application_End(), however, seems to be a necessity, as there is no C# equivalent of a static destructor/finalizer. As hacks go, this isn't that bad. It just smells a little funny.
Problem
I've gone rounds with this ever since I started programming classic ASP 12 (or so) years ago and I've never found a great solution because the architecture of ASP and ASP.NET has always been a swamp of bad practices, magic shared singletons, etc. My biggest issue is with the `HttpApplication` object with its non-event events (`Application_Start`, `Application_End`, etc.). If you want to do stuff once for the entire lifespan of an HTTP application, `Application_Start` is the obvious place to do it. Right? Not exactly. Firstly, this is not an event per se, it's a magic naming convention that, when followed, causes the method to be called once per AppDomain created by IIS. Besides magic naming conventions being a horrible practice, I've started to think it might be a reason there exist no such thing as a `Start` event on the `HttpApplication` object. So I've experimented with events that do exist, such as `Init`. Well, this isn't really an event either, it's an overridable method, which is the next best thing. It seems that the `Init()` method is called for every instantiation of an `HttpApplication` object, which happens a lot more than once per AppDomain. This means that I might as well just put my startup logic inside the `HttpApplication` object's constructor. Now my question is, why shouldn't I put my startup logic in the constructor? Why does even `Init()` exist and do I need to care about `Application_Start`? If I do, can anyone explain why there is no proper event or overridable method for this pseudo-event in the `HttpApplication` object? And can anyone explain to me why in a typical ASP.NET application, 8 instances of my `HttpApplication` are created (which causes the constructor and `Init` to run just as many times, of course; this can be mitigated with locking and a shared static boolean called `initialized`) when my application only has a single AppDomain?