class DelegateCommand : ICommand
    {
        protected readonly Predicate<object> _canExecute;
        protected readonly Action<object> _execute;

        public event EventHandler CanExecuteChanged;

        public DelegateCommand(Action<object> execute) : this(execute, _ => true) { }

        public DelegateCommand(Action<object> execute, Predicate<object> canExecute)
        {
            if (execute == null) throw new ArgumentNullException("execute");
            if (canExecute == null) throw new ArgumentNullException("canExecute");
            _execute = execute;
            _canExecute = canExecute;
        }

        public bool CanExecute(object parameter) { return _canExecute(parameter); }

        public void Execute(object parameter) { _execute(parameter); }

        public void RaiseCanExecuteChanged()
        {
            if (CanExecuteChanged != null)
                CanExecuteChanged.Invoke(this, EventArgs.Empty);
        }
    }