title: How to properly remap my XAML namespace?
body: <p>I have created a markup extension:</p>
  
  <pre><code>namespace Utils
  {
      public class CoolExtension : MarkupExtension
      {
          private string key;
  
          public CoolExtension ()
          {
          }
  
          public CoolExtension(string key)
          {
              this.key = key;
          }
  
          public override object ProvideValue(IServiceProvider serviceProvider)
          {
              return "!"+key+"!";
          }
      }
  }
  </code></pre>
  
  <p>Next, I added in the AssemblyInfo the XmlnsDefinitionAttribute to remap the namespace Utils to Default-Namespace, so that I don´t need a namespace to use the markup extension:</p>
  
  <pre><code>[assembly: XmlnsDefinitionAttribute("http://schemas.microsoft.com/winfx/2006/xaml/presentation", "Utils")]
  </code></pre>
  
  <p>Finally, in my window I used the extension:</p>
  
  <pre><code>&lt;Button Content="{Cool test}" /&gt;
  </code></pre>
  
  <p>The XAML-Editor don´t underline anything to show an error and the XAML-Designer shows the output as expected (a button with "!test!" as content). </p>
  
  <p>But it does not compile! In the error list I have the message that "Cool" wasn´t found in the namespace <a href="http://schemas.microsoft.com/" rel="nofollow">http://schemas.microsoft.com/</a></p>
  
  <p>What I´m doing wrong (to get rid of the namespace for my extension)? </p>