[ComVisible(false)]
    public abstract class CommandBase : ICommand
    {
        public virtual bool CanExecute(object parameter)
        {
            return true;
        }

        public abstract void Execute(object parameter);

        public event EventHandler CanExecuteChanged;
        protected void OnCanExecuteChanged()
        {
            var handler = CanExecuteChanged;
            if (handler != null)
            {
                handler.Invoke(this, EventArgs.Empty);
            }

    [ComVisible(false)]
    public class DelegateCommand : CommandBase
    {
        private readonly Predicate<object> _canExecute;
        private readonly Action<object> _execute;

        public DelegateCommand(Action<object> execute, Predicate<object> canExecute = null)
        {
            _canExecute = canExecute;
            _execute = execute;
        }

        private bool _canExecuteState;
        public override bool CanExecute(object parameter)
        {
            var previousState = _canExecuteState;