title: Silverlight - INotifyDataErrorInfo and complex property binding
body: <p>I have a view model implementing INotifyDataErrorInfo. I am binding a textbox to one of the view model properties like this:</p>
  
  <pre><code>&lt;TextBox Text="{Binding SelfAppraisal.DesiredGrowth, Mode=TwoWay, ValidatesOnNotifyDataErrors=True,NotifyOnValidationError=True}"  Height="200" 
                           TextWrapping="Wrap"/&gt;
  </code></pre>
  
  <p>The data binding works, but the UI is not responding when I add validation errors like this:</p>
  
  <pre><code>// validation failed
  foreach (var error in vf.Detail.Errors)
  {
      AddError(SelfAppraisalPropertyName + "." + error.PropertyName, error.ErrorMessage);
  }
  </code></pre>
  
  <p>After running <code>GetErrors("SelfAppraisal.DesiredGrowth")</code> in the immidiate window, I can see:
  <code>Count = 1<br>
  [0]: "Must be at least 500 characters. You typed 4 characters."</code></p>
  
  <p>I've made sure that the concatenation when adding an error matches the binding expression on the textbox, but the UI doesn't show messages as it was before I switched to using a complex type.</p>
  
  <p>What am I doing wrong? Does validation with INotifyDataErrorInfo support this?</p>
  
  <h2>Update</h2>
  
  <p>My viewmodel, which implements INotifyDataErrorInfo does raise ErrorsChanged when adding/removing errors.</p>
  
  <pre><code>protected void RaiseErrorsChanged(string propertyName)
      {
          if (ErrorsChanged != null)
          {
              ErrorsChanged(this, new DataErrorsChangedEventArgs(propertyName));
          }
      }
  </code></pre>