title: Optional parameter with UriTemplate
body: <p>I am building a wcf rest service to upload a file </p>
  
  <pre><code>[WebInvoke(Method = "POST", UriTemplate = "upload?fileName={fileName}&amp;filePath={filePath}&amp;replace={replace}")]
      void UploadFile(Stream fileContent, string fileName, string filePath, bool replace);
  </code></pre>
  
  <p>Here I need to make filePath &amp; replace parameter as optional. I can not simply rely on null check i.e. filePath = filePath ?? "" inside method if consumer doesn't pass the value for the parameter because first of all consumer doesn't know whether the parameters are required or optional. any help?</p>