PropertyObserver

The simplest observer, or monitor, in the Radical framework is a PropertyObserver the role of a property observer is to monitor property changes of a class implementing the INotifyPropertyChanged interface. We can monitor single properties:

var monitor = PropertyObserver.For( person )
    .Observe( p => p.FirstName )
    .Observe( p => p.LastName );

monitor.Changed += ( s, e ) => 
{
    //occurs when one of the properties change.
};

Or we can monitor the entire entity being notified each time a property changes:

var monitor = PropertyObserver.ForAllPropertiesOf( person );
monitor.Changed += ( s, e ) =>
{
    //occurs when one of the properties change.
};

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

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

In the above sample each time one of the property of the Person instance changes the command state will be evaluated for execution allowing the command to change its CanExecute state without polling anything but simply waiting to be notified.