Sometimes in the BizTalk forums such questions appear.
“…I have been using event log to test variables. I was hoping there was a way to watch it process in VS like you can debug a forms app.”

There is a difference in the usual app and in the “BizTalk app“.
When you start usual app it is exactly this app and you could debug it. When you “start” the BizTalk app that could means *many* *instances* of this BizTalk app could works simultaneously.
With BizTalk you have an intermediate layer, the host. This host (actually it is a host instance but it doesn’t matter for this case) manages the app *instances*. It could start many app instances simultaneously and then dehydrate, rehydrate, stop, abort them without our intervention.
Ideally we need to attach a debugger to exactly one app instance (which one?) or create a debugger working with many app instances simultaneously.
It is one of the source of the complexity of debugging the BizTalk apps.
BTW What is a BizTalk application at all?

Please, let me know, what do you think.