BrokerObserver

As for the PropertyObserver or the MementoObserver the BrokerObserver is an easy shortcut to react to message arrivals when using the message broker.

var broker = //instance of a IMessageBroker implementation.
var monitor = BrokerObserver.Using( broker )
    .WaitingFor<MySampleMessage>();

We can use a monitor to trigger, for example, the CanExecuteChanged event of a ICommand interface implementation:

var broker = //instance of a IMessageBroker implementation.
var monitor = BrokerObserver.Using( broker )
    .WaitingFor<MySampleMessage>();

DelegateCommand.Create()
    .OnCanExecute( state =>
    {
        //evaluate if the command can be executed.
        return true;
    } )
    .OnExecute( state =>
    {
        //execute the command
    } )
    .AddMonitor( monitor );

What the above code does is to trigger the CanExecuteChanged logic each time a message of type MySampleMessage is delivered via the monitored message broker.