A route named “x” is already in the route collection. Route names must be unique. Exception with ASP.NET MVC 3

Question

I\'m doing an ASP.NET MVC 3 web service and I keep getting this exception intermittently.

Stack trace:

Server Error in \'/\' Application.

A route n         


        

Answer 1

The routes get loaded from all assemblies within AppDomain.CurrentDomain, so if your old assemblies are still part of that, you might be still getting old/duplicate routes.

Answer 2

I was running an old MVC2 website and I got this issue because the IIS 'Managed Pipeline Mode' was set on 'Integrated' by default (press F4 on the project). Changing it to 'Classic' fixed the issue

Answer 3

This error can occur due to multiple causes, I had the same error and solved it by modifying the Global.asax class.

The Application_Start method at Global.asax.cs was like:

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
}

The following line occurs twice in this method:

RouteConfig.RegisterRoutes(RouteTable.Routes);

This ensured that the route was twice added to the route list and at the same time causing the error.

I changed the Application_Start method as follows and the error disappeared:

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
}

This may not be the answer for your problem, but can perhaps help others in the future. I didn't see this answer between the others, so I decided to add this.

Answer 4

I had an application that was a Forms app migrated to MVC with a third party component used for authentication which redirected to another site. The component would start a session twice if the user wasn't already logged in (once for initial connection to site and once for return). So I solved this with the following code:

if (routes.Count < 3)
            {
                routes.IgnoreRoute("login.aspx");
                routes.IgnoreRoute("default.aspx");
                routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

                routes.MapRoute(
                    name: "Default",
                    url: "{controller}/{action}/{id}",
                    defaults: new {action = "Index", id = UrlParameter.Optional}
                    );
            }