Migrating Mvc Routing

ASP.NET MVC Routing Migration

Migrate ASP.NET MVC routing from RouteCollection/RouteConfig.cs to ASP.NET Core endpoint routing in Program.cs.

Workflow

Migration Progress:
- [ ] Step 1: Locate route registration
- [ ] Step 2: Convert to ASP.NET Core routing
- [ ] Step 3: Handle MVC + API controllers
- [ ] Step 4: Preserve existing customizations
- [ ] Step 5: Remove RouteConfig

Step 1: Locate Route Registration

Find all route registration code. Typically lives in RouteConfig.cs:

public class RouteConfig
{
    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.MapMvcAttributeRoutes();
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Catalog", action = "Index", id = UrlParameter.Optional }
        );
    }
}

Step 2: Convert to ASP.NET Core Routing

Default routes (no customization): Replace with:

app.MapDefaultControllerRoute();

Custom routes: Add MapControllerRoute calls in Program.cs. Inline defaults and optional parameters into the pattern string because ASP.NET Core uses pattern tokens instead of a separate defaults object:

// Old: url: "{controller}/{action}/{id}", defaults: new { controller = "Catalog", action = "Index", id = UrlParameter.Optional }
// New:
app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Catalog}/{action=Index}/{id?}");

Route Pattern Conversion Reference

| Old (RouteCollection) | New (ASP.NET Core) |

|-----------------------|--------------------|

| url: "{controller}/{action}/{id}" | pattern: "{controller}/{action}/{id?}" |

| defaults: new { controller = "Home" } | pattern: "{controller=Home}" |

| defaults: new { action = "Index" } | pattern: "{action=Index}" |

| id = UrlParameter.Optional | {id?} |

| routes.MapMvcAttributeRoutes() | app.MapControllers() |

Step 3: Handle MVC + API Controllers

If the project has both MVC and API controllers, register both attribute and conventional routing. Call app.MapControllers() before app.MapControllerRoute() so attribute-routed API controllers take precedence over conventional routes — otherwise conventional routes could intercept API requests:

app.MapControllers(); // Attribute routing for API controllers
app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

Step 4: Preserve Existing Customizations

Keep any existing routing middleware on the application object and add new routes alongside it. Carry over method-chained customizations like .RequireSystemWebAdapterSession():

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}")
    .RequireSystemWebAdapterSession();

Step 5: Remove RouteConfig

• Delete RouteConfig.cs (or equivalent file containing RegisterRoutes). Only delete if it contains no non-routing logic.
• Remove all references to RouteTable.Routes across the codebase.
• Clean up orphaned using statements and class references.

Success Criteria

• All routes migrated to Program.cs with correct pattern syntax
• Both attribute and conventional routing configured when needed
• RouteConfig.cs removed and no RouteTable.Routes references remain
• Project builds without errors