Async friendly DispatcherTimer wrapper/subclass
问题 I have a DispatcherTimer running in my code that fire every 30 seconds to update system status from the server. The timer fires in the client even if I'm debugging my server code so if I've been debugging for 5 minutes I may end up with a dozen timeouts in the client. Finally decided I needed to fix this so looking to make a more async / await friendly DispatcherTimer. Code running in DispatcherTimer must be configurable whether it is reentrant or not (i.e. if the task is already running it