// use this when the command is owned by the source object - i.e. we aren't concerned about their relative lifespans
public static perCommandBase ObservesInternalProperty(this perCommandBase command, INotifyPropertyChanged source, string propertyName)
{
source.PropertyChanged += (s, e) =>
{
if (string.Equals(e.PropertyName, propertyName, StringComparison.InvariantCultureIgnoreCase))
{
command.RaiseCanExecuteChanged();
}
};
return(command);
}
public static perCommandBase ObservesCollection(this perCommandBase command, INotifyCollectionChanged collection)
{
collection.CollectionChanged += (s, e) => command.RaiseCanExecuteChanged();
return(command);
}
// use this when the command is owned by an object (ViewModel) other than the source object
// i.e. we need to take account of their relative lifespans - in particular if the source object is live for the whole application runtime
public static perCommandBase ObservesExternalProperty(this perCommandBase command, INotifyPropertyChanged source, string propertyName)
{
perWeakPropertyChangedEventHandler.Register(source, propertyName, command, (listener, sender, args) => listener.RaiseCanExecuteChanged());
return(command);
}
