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 named 'ListTables' is already in the route collection. Route names must be unique.
Parameter name: name

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.ArgumentException: A route named 'ListTables' is already in the route collection. Route names must be unique.
Parameter name: name

Source Error: 


Line 24:            //     }
Line 25:            // );
Line 26:             context.MapRoute(
Line 27:                 "ListTables",
Line 28:                 // example: 

Source File: C:\inetpub\wwwroot\SchemaBrowserService\Website\Areas\Api\ApiAreaRegistration.cs    Line: 26 

Stack Trace: 


[ArgumentException: A route named 'ListTables' is already in the route collection. Route names must be unique.
Parameter name: name]
   System.Web.Routing.RouteCollection.Add(String name, RouteBase item) +2329682
   System.Web.Mvc.RouteCollectionExtensions.MapRoute(RouteCollection routes, String name, String url, Object defaults, Object constraints, String[] namespaces) +236
   System.Web.Mvc.AreaRegistrationContext.MapRoute(String name, String url, Object defaults, Object constraints, String[] namespaces) +59
   System.Web.Mvc.AreaRegistrationContext.MapRoute(String name, String url, Object defaults) +17
   SchemaBrowserService.Areas.Api.ApiAreaRegistration.RegisterArea(AreaRegistrationContext context) in C:\inetpub\wwwroot\SchemaBrowserService\Website\Areas\Api\ApiAreaRegistration.cs:26
   System.Web.Mvc.AreaRegistration.CreateContextAndRegister(RouteCollection routes, Object state) +105
   System.Web.Mvc.AreaRegistration.RegisterAllAreas(RouteCollection routes, IBuildManager buildManager, Object state) +199
   System.Web.Mvc.AreaRegistration.RegisterAllAreas(Object state) +45
   System.Web.Mvc.AreaRegistration.RegisterAllAreas() +6
   Website.MvcApplication.Application_Start() in C:\Users\djackson\Downloads\RestApiMvc3\Website\Website\Global.asax.cs:35

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.272

It's probably related to the fact that Route Debugger shows that I have some old routes that I've modified or deleted and won't go away (even after rebooting my machine). The stack trace also refers to a source file that has long since been deleted and my app has been moved to a new location, cleaned and rebuilt since then. What am I missing?

Here is all of my route registration code:

// in Global.asax.cs:
public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
    routes.MapRoute(
        "Default2", // Route name
        "Api/{controller}/{action}/{id}", // URL with parameters
        new { controller = "DataSource", action = "Index", area = "Api", id = UrlParameter.Optional } // Parameter defaults
        );

        routes.MapRoute(
            "Default", // Route name
            "{controller}/{action}/{id}", // URL with parameters
            new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
        );

    }

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    RegisterRoutes(RouteTable.Routes);
}

// in ApiAreaRegistration.cs:
public class ApiAreaRegistration : AreaRegistration
{
    public override string AreaName { get { return "Api"; } }

    public override void RegisterArea(AreaRegistrationContext context)
    {
        // DataSources

        // Tables
        context.MapRoute(
            "ListTables",
            // example: 
            // /api/DataSources/DataSource/1/schemata/schema/dbo/tables
               "Api/DataSources/DataSource/{dataSourceId}/schemata/{schemaName}/tables",
            new
            {
                controller = "Tables",
                action = "TableList",
                schemaName = "dbo",
                dataSourceId = "DefaultId"
            }
        );


        // Schemata
        context.MapRoute(
          "Schema",
            // example: 
            // /api/DataSources/DataSource/1/schemata/schema/dbo
              "Api/DataSources/DataSource/{dataSourceId}/schemata/{schemaName}",
          new
          {
              controller = "Schema",
              action = "Schema",
              dataSourceId = "DefaultId",
              schemaName = UrlParameter.Optional
          }
       );

       // // DataSources
        context.MapRoute(
            "SingleDataSource",
            "Api/DataSources/DataSource/{dataSourceId}",
            new
            {
                controller = "DataSource",
                action = "DataSource",
                dataSourceId = UrlParameter.Optional
            }
        );
        context.MapRoute(
            "ListDataSources",
            "Api/DataSources",
            new
            {
                controller = "DataSource",
                action = "DataSourceList",
                dataSourceId = "DefaultId"
            }
        );
        context.MapRoute(
             "Api_default",
             "Api/{controller}/{action}/{id}",
             new { action = "Index", id = UrlParameter.Optional }
        );

    }
}

Answer 1

To fix this problem I had to go into the bin folder on my project, delete all DLL files and then rebuild and this fixed the problem.

Answer 2

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 3

I found out that Global.asax was referring to an old version of the site's DLL file before I renamed it. The DLL was not being cleaned up when I did Build > Clean up because the VS project/solution didn't refer to it any more. It seems that sometimes only the newer version of the DLL was being used, allowing the site to work correctly, but eventually both of them would be loaded causing the route conflicts.

Answer 4

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.