title: StaticResource not found for key TextToBoolConverter
body: <p>I have a problem with a converter I need to use on a Comment text.</p>
  
  <p>I get: "StaticResource not found for key TextToBoolConverter". </p>
  
  <p>Converter:</p>
  
  <pre><code>namespace myMood.Helpers
  {
      public class TextToBoolConverter : IValueConverter
      {
          public object Convert(object value, Type targetType, 
                                    object parameter, CultureInfo culture)
          {
              if (value != null)
                  if (!(value is string)) return true;
              return string.IsNullOrWhiteSpace(value as string) ? false : true;
          }
  
          public object ConvertBack(object value, Type targetType, 
                object parameter, CultureInfo culture)
          {
              throw new NotImplementedException();
          }
      }
  }
  </code></pre>
  
  <p>View:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
  &lt;ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
               xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
               x:Class="myMood.Views.Entries"
               Icon="ic_view_headline_white_24dp.png"
               xmlns:converters="clr-namespace:myMood.Helpers"
               xmlns:viewModels="clr-namespace:myMood.ViewModels"&gt;
  ...
  &lt;Label Text="{Binding Comment}" 
        IsVisible="{Binding Comment, Converter={StaticResource TextToBoolConverter}}"&gt;
  </code></pre>