During an invocation, methods are invoked in the order in which they appear in the invocation list. A delegate attempts to invoke every method in its invocation list; duplicates are invoked once for each time they appear in the invocation list. …-snip- … When the signature includes a parameter that is passed by reference, the final value of the parameter is the result of every method in the invocation list executing sequentially and updating the parameter’s value.
You can have multiple handlers. They are executed in the order they are registered.