title: IValueConverter.Convert doesn't get called on a OneWay bind
body: <p>I have a boolean property (that does called <code>INotifyPropertyChanged</code> in the setter) that is bound to a button.IsEnabled property in my XAML. Currently I'm using a <code>TwoWay</code> binding, but this is causing problems and I only need a <code>OneWay</code> binding. My problem is that the converter I'm using doesn't get called beyond the first time the program starts up. I've put breakpoints in the setter and it gets called loads, but the <code>Convert()</code> method doesn't get called at all. Why is this?</p>
  
  <p>Some code:</p>
  
  <pre><code>public bool IsSaving
      {
          get
          {
              return _isSaving;
          }
          set
          {
              _isSaving = value;
              NotifyOfPropertyChange(() =&gt; IsSaving);
          }
      }
  </code></pre>
  
  <p>and the XAML:</p>
  
  <pre><code>IsEnabled="{Binding Path=IsSaving, Mode=OneWay, Converter={StaticResource booleanToNotEnabledConverter}}"
  </code></pre>
  
  <p>The converter really just returns <code>!(bool)value</code> so the button gets disabled when <code>IsSaving</code> is true.</p>