Important: be very careful about subscribing to a static event from instances. Static-to-static is fine, but a subscription from a static event to an instance handler is a great (read: very dangerous) way to keep that instance alive forever. GC will see the link, and will not collect the instance unless you unsubscribe (or use something like a WeakReference).
The pattern for creating static events is the same as instance events, just with static:
public static event EventHandler SomeEvent;
To make life easier (re null checking), a useful trick here is to add a trivial handler:
public static event EventHandler SomeEvent = delegate {};
Then you can simply invoke it without the null-check:
SomeEvent(null, EventArgs.Empty);
Note that because delegate instances are immutable, and de-referencing is thread-safe, there is never a race condition here, and no need to lock… who-ever is subscribed when we de-reference gets invoked.
(adjust for your own event-args etc).
This trick applies equally to instance events.