title: ASP.NET MVC MapRoute: An item with the same key has already been added
body: <p>I am working on an application which uses a Web Service. This web service uses the MVC Framework for .NET. </p>
  
  <p>In the web service, I added extra parameters to a method in the controller, and therefore changed the Global.asax.cs file to add those parameters to the specific method's route. However, when I run the application now, I get the error:</p>
  
  <blockquote>
    <p><em>ArgumentException was unhandled by user code: An item with the same key has already been added.</em></p>
  </blockquote>
  
  <p>I did not create another MapRoute, I just updated the existing MapRoute for that specific method to have extra parameters.</p>
  
  <p>Do I have to do anything else with the routing or another file after I change the number of parameters in a method in the controller? </p>
  
  <p>Why would I be getting a same key issue when there is only one MapRoute to that method name?</p>