Passing a parameter to ICommand

Question

I have a simple button that uses a command when executed, this is all working fine but I would like to pass a text parameter when the button is clicked.

I think my XAML is ok, but I'm unsure how to edit my RelayCommand class to receive a parameter:

<Button x:Name="AddCommand" Content="Add" 
    Command="{Binding AddPhoneCommand}"
    CommandParameter="{Binding Text, ElementName=txtAddPhone}" />

public class RelayCommand : ICommand
{
    private readonly Action _handler;
    private bool _isEnabled;

    public RelayCommand(Action handler)
    {
        _handler = handler;
    }

    public bool IsEnabled
    {
        get { return _isEnabled; }
        set
        {
            if (value != _isEnabled)
            {
                _isEnabled = value;
                if (CanExecuteChanged != null)
                {
                    CanExecuteChanged(this, EventArgs.Empty);
                }
            }
        }
    }

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

    public event EventHandler CanExecuteChanged;

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

Answer 1

Change Action to Action<T> so that it takes a parameter (probably just Action<object> is easiest).

private readonly Action<object> _handler;

And then simply pass it the parameter:

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