/// <summary>
/// Observes a property that implements INotifyPropertyChanged, and automatically calls DelegateCommandBase.RaiseCanExecuteChanged on property changed notifications.
/// </summary>
/// <typeparam name="T">The object type containing the property specified in the expression.</typeparam>
/// <param name="propertyExpression">The property expression. Example: ObservesProperty(() => PropertyName).</param>
protected internal void ObservesPropertyInternal <T>(Expression <Func <T> > propertyExpression)
{
if (_observedPropertiesExpressions.Contains(propertyExpression.ToString()))
{
throw new ArgumentException($"{propertyExpression.ToString()} is already being observed.",
nameof(propertyExpression));
}
else
{
_observedPropertiesExpressions.Add(propertyExpression.ToString());
PropertyObserver.Observes(propertyExpression, RaiseCanExecuteChanged);
}
}
/// <summary>
/// Initiate PropertyObserverNode for a given property expression.
/// </summary>
/// <param name="propertyExpression">Expression representing property to be observed.</param>
/// <param name="action">Action to be invoked when PropertyChanged event occours.</param>
/// <param name="propertyObserver">PropertyObserver instance which owns registered event handlers.</param>
internal static void Observes(Expression propertyExpression, Action action, PropertyObserver propertyObserver)
{
new PropertyObserverNode(propertyExpression, action, propertyObserver);
}
private PropertyObserverNode(Expression propertyExpression, Action action, PropertyObserver propertyObserver)
{
_action = action;
_propertyObserver = propertyObserver;
SubscribeListeners(propertyExpression as MemberExpression);
}
