title: Xamarin.Forms MarkupExtension for binding
body: <p>I want to make markup extension to simplify bidning.
  I have dictionary and I bind that property to a Label in the view.
  I have ValueConverter that takes this dictinary and I pass ConverterParameter which is a string and it finds </p>
  
  <pre><code>&lt;Label Text="{Binding Tanslations,Converter={StaticResource TranslationWithKeyConverter}, ConverterParameter='Test'}"/&gt;
  </code></pre>
  
  <p>but I have to do same thing for different labels but the key (ConverterParameter) will be different, the rest will remain same</p>
  
  <p>I want a markupextension that will allow me to write this:</p>
  
  <pre><code>&lt;Label Text="{local:MyMarkup Key=Test}"/&gt;
  </code></pre>
  
  <p>this markup should generate binding to the property named "Tanslations" with valueconverter of TranslationWithKeyConverter and ConverterParameter with value of Key.</p>
  
  <p>I tried to do it but it does not work:</p>
  
  <pre><code>public class WordByKey : IMarkupExtension
  {
      public string Key { get; set; }
      public object ProvideValue(IServiceProvider serviceProvider)
      {
          return new Binding("Tanslations", BindingMode.OneWay, converter: new TranslationWithKeyConverter(), converterParameter: Key);
      }
  }
  </code></pre>
  
  <p>nothing is displayed on the label.</p>