title: How to use RelayCommand with the MVVM Light framework
body: <p>I've just started learning the MVVM Light framework and I can't find any straightforward examples on how to use a RelayCommand. For purposes of learning, I'd just like to have a button in my view which when clicked show's a hello world world message box, and which is enabled on every even minute (basically if DateTime.Now.Minute % 2 == 0).</p>
  
  <p>How would the button XAML look and how would the RelayCommand HelloWorld be defined in the ViewModel?</p>
  
  <p>Thanks for your help!!</p>