[MVVM] RelayCommand

A continuación comparto una implementación del RelayCommand que estoy usando para trabajar con MVVM y PCL (Portable Class Library).

IRelayCommand.cs

    public interface IRelayCommand : ICommand
    {
        void RaiseCanExecuteChanged();
    }

RelayCommand class

    public class RelayCommand : IRelayCommand
    {
        #region Fields

        private readonly Action _execute;
        private readonly Func<bool> _canExecute;

        #endregion Fields

        #region Constructors

        public RelayCommand(Action execute)
            : this(execute, null)
        {
        }

        public RelayCommand(Action execute, Func<bool> canExecute)
        {
            _execute = execute;
            _canExecute = canExecute;
        }

        #endregion Constructors

        #region ICommand Members

        public bool CanExecute(object parameter)
        {
            return null == _canExecute ? true : _canExecute();
        }

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

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

        public event EventHandler CanExecuteChanged;

        #endregion ICommand Members
    }

RelayCommand<T> class

    public class RelayCommand<T> : IRelayCommand
    {
        #region Fields

        private readonly Action<T> _execute;
        private readonly Func<T, bool> _canExecute;

        #endregion Fields

        #region Constructors

        public RelayCommand(Action<T> execute)
            : this(execute, null)
        {
        }

        public RelayCommand(Action<T> execute, Func<T, bool> canExecute)
        {
            _execute = execute;
            _canExecute = canExecute;
        }

        #endregion Constructors

        #region ICommand Members

        public bool CanExecute(object parameter)
        {
            parameter = null == parameter ? default(T) : parameter;
            return null == _canExecute ? true : _canExecute((T)parameter);
        }

        public void Execute(object parameter)
        {
            parameter = null == parameter ? default(T) : parameter;
            _execute((T)parameter);
        }

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

        public event EventHandler CanExecuteChanged;

        #endregion ICommand Members
    }

¿Como usar?

        #region Command Members

        private RelayCommand aceptarCommand;

        #endregion Command Members

        #region Command Properties

        public RelayCommand AceptarCommand
        {
            get
            {
                if (null == aceptarCommand)
                    aceptarCommand = new RelayCommand(AceptarExecute, AceptarCanExecute);

                return aceptarCommand;
            }
        }

        #endregion Command Properties

        #region Command Methods

        private bool AceptarCanExecute()
        {
            return true;
        }

        private void AceptarExecute()
        {
        }

        #endregion Command Methods