title: Issue with MVC Core routing
body: <p>I have an MVC core site with the default route set up:</p>
  
  <pre><code>public void Configure(IApplicationBuilder app)
  {
      app.UseMvcWithDefaultRoute();
  }
  </code></pre>
  
  <p>which creates rule {controller=Home}/{action=Index}/{id?}</p>
  
  <p>I have a link that is generated using a tag helper like so.</p>
  
  <pre><code> &lt;a asp-controller="Help" asp-action="privacy-policy" asp-route-id="@Model.id" target="_blank"&gt;
          privacy policy
      &lt;/a&gt;
  </code></pre>
  
  <p>This generates the following link:</p>
  
  <pre><code>http://localhost:63110/help/privacy-policy/9b933739-15d0-4c60-a84e-29f596a179d4
  </code></pre>
  
  <p>But clicking it I get a 404</p>
  
  <pre><code>[Route("help")]
  public class HelpController : Controller
  {
   [HttpGet("privacy-policy")]
   public async Task&lt;IActionResult&gt; PrivacyPolicy(string id)
   {
     // stuff
   }
  }
  </code></pre>
  
  <p>What have i done wrong.</p>