define a ToolTip Style that hides a tooltip if Converter(ToolTip) returns fale
<p>I want to hide empty ToolTips</p>

<p>this is what worked up to a certain Point:</p>

<pre><code>  &lt;Style TargetType="ToolTip"&gt;
    &lt;Style.Triggers&gt;
      &lt;Trigger Property="Content"
                 Value="{x:Static sys:String.Empty}"&gt;
        &lt;Setter Property="Visibility"
                    Value="Collapsed" /&gt;
      &lt;/Trigger&gt;
      &lt;Trigger Property="Content"
                 Value="{x:Null}"&gt;
        &lt;Setter Property="Visibility"
                    Value="Collapsed" /&gt;
      &lt;/Trigger&gt;
    &lt;/Style.Triggers&gt;
  &lt;/Style&gt;
</code></pre>

<p>Problem is: Trigger only operates on null or string.IsEmpty
I want to catch whitespace tooltips as well.</p>

<p>so I tried:</p>

<pre><code>  &lt;Style TargetType="ToolTip"&gt;
    &lt;Setter Property="Visibility"&gt;
      &lt;Setter.Value&gt;
        &lt;Binding &gt;   &lt;!------------ what comes here? --&gt;
          &lt;Binding.Converter&gt;
            &lt;loc:NotEmptyToVisibilityConverterEx/&gt;
          &lt;/Binding.Converter&gt;
        &lt;/Binding&gt;
      &lt;/Setter.Value&gt;
    &lt;/Setter&gt;
  &lt;/Style&gt;
</code></pre>

<p>My Problem is, I'm not able to (dunno how) access the actual tooltip text.</p>

<pre><code>  [ValueConversion(typeof(string), typeof(Visibility))]
  public class NotEmptyToVisibilityConverterEx : IValueConverter {
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture) {
      var visible = !string.IsNullOrEmpty(((string) value).Trim());
      return visible ? Visibility.Visible : Visibility.Collapsed;
    }
  }
</code></pre>

<p>Anybody have an idea?</p>