Question

I want to run some tests when my ASP.NET webapp comes online (preferably before anyone tries to access it), to make sure all of my runtime dependencies are available as I expect them to be.

When is a good time to perform these tests (e.g. Application_Start, Application_Init, somewhere else, etc), and what’s a good technique for making my webapp unavailable to users if my tests fail (it shares an app pool with other apps I don’t want to affect)?

Answer 1

One approach would be to put your checks in the Application_Start event, and update a static property (or properties) in the Global class with the result of your test.

If you’re using master pages, each master page (I’ve personally never seen more than 2 base master classes in a project) could check the static property in the Global class, and redirect to an “app offline” page if appropriate. Since the static property would only be updated when the application started, there shouldn’t be any performance impact.

The code in your master page’s OnLoad event might look like this…

if (!Global.WasDependencyCheckSuccessful)
{
//redirect to error page
}

If you’re not using master pages, this may not be the best solution (because you would need to update each web form in your site individually).