RelayCommand's reference is not found

RelayCommand is a class created by MS for handling event or command in WPF. you can create own class or go through below link.

http://msdn.microsoft.com/en-us/magazine/dd419663.aspx

This does not necessarily have to be RelayCommand it's simply a name of class from most common example on the web.

The mechanism of ICommand works in a way that instead of getter or setter being called you get public void Execute(object parameter) to be called on class that is implementing ICommand

Let me give you an example:

I have a hyperlink which when clicked should do some stuff before redirecting person to browser.

XAML

<Hyperlink NavigateUri="https://payments.epdq.co.uk/ncol/prod/backoffice/"     Command="{Binding Path=NavigateToTakePayment}"  IsEnabled="{Binding CanTakePayment}">     Launch Payments Portal</Hyperlink>

now in viewModel I have property

public ICommand NavigateToTakePayment       {    get { return _navigateToTakePayment ?? (_navigateToTakePayment = new NavigateToTakePaymentCommand(this)); }    set { _navigateToTakePayment = value; }}

but when hyperlink is clicked instead of getter being fired like one would expect NavigateToTakePaymentCommand class Execute method is fired instead.

  public class NavigateToTakePaymentCommand : ICommand  {        public NavigateToTakePaymentCommand(PaymentViewModel paymentViewModel)        {            ViewModel = paymentViewModel;        }        public PaymentViewModel ViewModel { get; set; }        public bool CanExecute(object parameter)        {            return true;        }        public void Execute(object parameter)        {         //your implementation stuff goes here.        }        public event EventHandler CanExecuteChanged;  }

I hope this example will clarify how the mechanism works and will save you some time.