title: WPF Validation Framework
body: <p>Given the following requirements:</p>
  
  <ul>
  <li>WPF Application</li>
  <li>MVVM Pattern</li>
  <li>Validatable viewmodels
  <ul>
  <li>with nested (validatable) viewmodels</li>
  <li>with nested Collections of (validatable) viewmodels</li>
  </ul></li>
  <li>WPF Controls which become disabled on validation errors
  <ul>
  <li>e.g. Binding Views IsEnabled to IsValid-Property in Viewmodels</li>
  </ul></li>
  </ul>
  
  <p>Is there any built-in or third-party validation framework available for WPF, or do I have to write one on my own? I've given IDataErrorInfo a try, but I failed when it came to validating nested viewmodels or entire collections.</p>
  
  <p>Thanks!</p>