title: Validation When Using MVVM (WPF) with a DDD-Based Model
body: <p>A common MVVM/WPF approach is to data-bind the UI's controls directly to the underlying model object. The model object may contain its own validation logic (perhaps exposed via IDataErrorInfo) or may be validated by a helper class checks a model object instance for errors. In either case, at times the model have invalid data in it and so be in an invalid state.</p>
  
  <p>However, in the DDD world, the model is never to be in an invalid state. How do you suggest performing validation when using WPF and DDD? </p>
  
  <p>Thanks,<br>
  Ben</p>